DIN 18041-2004 Eng [PDF]

Zitiervorschau

DEUTSCHE NORM

May 2004

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DIN 18041 ICS 17.140.01

Supersedes DIN 18041:1968-10

Acoustic quality in small to medium-sized rooms

Hörsamkeit in kleinen bis mittelgroßen Räumen

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Document comprises 35 pages

Translation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text.

©

No part of this translation may be reproduced without prior permission of DIN Deutsches Institut für Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, for German Standards (DIN-Normen).

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DIN 18041:2004-05

Contents

Page

Foreword..............................................................................................................................................................3 1

Scope ......................................................................................................................................................4

2

Normative references ............................................................................................................................4

3

Terms and definitions ...........................................................................................................................5

4 4.1 4.2 4.2.1 4.2.2 4.3 4.3.1 4.3.2 4.4 4.5 4.5.1 4.5.2 4.5.3 4.5.4

Requirements for acoustic quality over medium and large distances (group A rooms) ...............9 General....................................................................................................................................................9 Building acoustics requirements ...................................................................................................... 10 Background noise............................................................................................................................... 10 Structural noise control ..................................................................................................................... 11 Room acoustics parameters.............................................................................................................. 11 Volume index....................................................................................................................................... 11 Reverberation time ............................................................................................................................. 11 Room geometry................................................................................................................................... 14 Electro-acoustic sound systems for spoken presentations .......................................................... 15 Selection criteria ................................................................................................................................. 15 Direct sound amplification by means of electro-acoustic sound systems .................................. 17 Announcement systems, alarm systems ......................................................................................... 17 Sound systems for the hearing impaired......................................................................................... 17

5

Measures to ensure high acoustic quality over medium and larger distances (group A rooms).................................................................................................................................................. 18 General measures............................................................................................................................... 18 Spatial arrangement of rooms........................................................................................................... 18 Noise in the room that is being used................................................................................................ 18 Specific design measures.................................................................................................................. 18 Small rooms with volumes up to about 250 m3 ............................................................................... 18 Medium-sized rooms and small halls with volumes from about 250 m3 to 5 000 m3 ................. 20 Special cases ...................................................................................................................................... 22

5.1 5.1.1 5.1.2 5.2 5.2.1 5.2.2 5.2.3 6

Recommendations and measures to ensure acoustic quality in rooms over smaller distances (group B rooms) ................................................................................................................ 22 General................................................................................................................................................. 22 Measures ............................................................................................................................................. 22

6.1 6.2

Annex A (informative) Terms relating to speech intelligibility .................................................................... 25 Annex B (informative) Describing the sound absorption of materials, structures, objects and people (examples)............................................................................................................................... 28 Annex C (informative) Measures for improving speech intelligibility for the hearing impaired .............. 30 Annex D (informative) Spoken communication ............................................................................................ 33 Bibliography ..................................................................................................................................................... 35

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2

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DIN 18041:2004-05

Foreword The acoustic quality of a room, in the sense of this standard, is essentially determined by the location of the room in the building, the sound insulation of the components surrounding it, noise generated by building equipment, as well as the shape and size of the room (primary structure) and the surface properties of the boundary surfaces and furnishings (secondary structure). At the same time the dimensions and spatial distribution of sound absorptive and sound reflecting surfaces in the room concerned are also important influence factors. NOTE When designing rooms used primarily for spoken communication, the interests of people with impaired hearing (hard-of-hearing or deaf persons) are to be taken into account [1]. Here the “ban on prejudicial treatment” laid down in Article 3, Clause 3 of the German Grundgesetz (German Basic Law), and Article 4 of the Bundesgleichstellungsgesetz (German Federal Equal Opportunities Act) of 1 May 2002 apply. In the 1968 edition of this standard, these interests were not taken into account. In addition to the general need for updating, this is one of the most important reasons for the revision of the standard. Moreover, since the publication of the 1968 edition, electro-acoustic equipment has developed considerably and is today part of the standard equipment of many rooms, particularly as a result of the widespread adoption of media technology. Because room acoustics and electroacoustics are interdependent, fundamental guidelines and recommendations regarding spoken presentations have been included in this standard.

Amendments This standard differs from DIN 18041:1968-10 as follows: a)

Terms and definitions have been revised and expanded.

b)

Particular consideration has been given to persons with impaired hearing.

c)

Recommendations for electro-acoustic sound systems are now included.

d)

Guideline values for the frequency dependence of reverberation times are given.

e)

Annexes A to D have been included to cover: —

parameters relating to speech intelligibility;

—

describing the sound absorption of materials, structures, objects and people;

—

measures for improving speech intelligibility for the hearing impaired;

—

spoken communication.

Previous editions DIN 18041: 1968-10

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DIN 18041:2004-05

1

Scope

This standard applies to small to medium-sized rooms with a room volume up to about 5 000 m3, and to sports halls and swimming baths without public present up to 8 500 m3 in volume. It specifies acoustic requirements and design guidelines to ensure good acoustic quality, primarily of spoken communication, in such rooms. In this standard a differentiation is made between acoustic quality over —

medium and large distances (group A rooms), for instance in conference rooms, courtrooms, council chambers and function rooms, classrooms, seminar rooms, lecture theatres, convention rooms and interaction rooms, group rooms in nursery schools and children’s day care centres, senior day care centres, community rooms, sports halls, swimming baths, and

—

small distances (group B rooms), for instance in sales rooms, eating places, public areas for short- and long-distance public transportation, ticket desks and bank counters, consulting rooms in solicitors’ and doctors’ practices, office areas, municipal public offices, operating theatres, treatment rooms, sick rooms, rehabilitation rooms, workrooms (e.g. training workshops), public areas, libraries and reading rooms. --``,,,,`,``,``,`,``,```````,`,`-`-`,,`,,`,`,,`---

NOTE 1 In group A rooms as in this standard, the acoustic quality over smaller distances is also ensured. However, in group B rooms, the acoustic quality over greater distances is severely limited.

The standard does not cover the acoustic quality of rooms with special requirements, such as theatres, concert halls, cinemas, sacred spaces, or in rooms for the high-quality recording of music and speech (e.g. studios, central control rooms for radio, film, television and sound storage media productions). However, this standard can be applied by analogy to rooms for general musical presentations, multipurpose rooms (e.g. town halls) and all rooms with a large volume up to about 30 000 m3. NOTE 2 As a rule, the needs of people with impaired hearing are to be considered at the design stage. It should be borne in mind that spoken communication not only takes place in “function rooms”, but in all locations where people congregate.

The standard addresses architects, building designers, building owners, and specialist engineers who are involved in the planning and construction of rooms covered by this standard.

2

Normative references

This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to (including any amendments) applies. DIN 4109:1989-11, Sound insulation in buildings — Requirements and testing DIN 45635-60, Measurement of airborne noise emitted by machines — Enveloping surface method — Pneumatic tools and machines DIN 45641, Averaging of sound levels DIN 52219, Tests in building acoustics — Field measurements of noise emitted by water and drainage installations DIN EN 457, Safety of machinery — Auditory danger signals — General requirements, design and testing (ISO 7731:1986, modified)

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DIN 18041:2004-05

E DIN EN 12354-6:2002-03, Building acoustics — Estimation of acoustic performance of buildings from the performance of elements — Part 6: Sound absorption in enclosed spaces DIN EN 20354, Acoustics — Measurement of sound absorption in a reverberation room (ISO 354:1985) DIN EN 60118-4:1999-08, Hearing aids — Part 4: Magnetic field strength in audio-frequency induction loops for hearing aid purposes (IEC 60118-4:1981 + A1:1998) DIN EN 60849 (VDE 0828 Part 1), Sound systems for emergency purposes (IEC 60849:1998) DIN EN ISO 3382, Acoustics — Measurement of the reverberation time of rooms with reference to other acoustical parameters (ISO 3382:1997) DIN EN ISO 3746, Acoustics — Determination of sound power levels of noise sources using sound pressure — Survey method using an enveloping measurement surface over a reflecting plane (ISO 3746:1995) DIN EN ISO 11654, Acoustics — Sound absorbers for use in buildings — Rating of sound absorption (ISO 11654:1997) ISO 10996:1999-03, Photography — Still-picture projectors — Determination of noise emissions VDI 3760:1996-02, Calculation and measurement of sound propagation in workrooms

3

Terms and definitions

For the purposes of this standard, the following terms and definitions apply. 3.1 acoustic quality suitability of a room for particular audio presentations, in particular for spoken communication and musical presentation at the locations provided in the room. The acoustic quality of a room is predominantly influenced by room geometry, the selection and distribution of sound absorptive and sound reflecting surfaces, the reverberation time, and the total noise pressure level 3.2 speech sound pressure level LSA equivalent A-weighted sound pressure level of speech measured at the ear of the listener. The magnitude of the speech sound pressure level measured at a 1 m distance from the speaker is denoted by LpA,1m and characterizes the manner of speech of the speaker NOTE 1 The A-weighted speech sound pressure level, LSA, and LpA,1m are measured while the person is speaking, and are expressed in decibels averaged over this time. NOTE 2 As a rule, sound levels are expressed in decibels (dB). It is common practice, however, to express A-weighted decibels as dB(A) or dbA.

3.3 spoken communication transmission or exchange of information for understanding between people via messages by means of the spoken language, possibly with the aid of facial expressions and gestures NOTE Components of spoken communication are the speaker (natural sound source) or the sound transducer that produces the spoken messages, and the listener (receiver) who hears and understands them. Criteria for spoken communication are the properties of the sound source (sound power level of the speaker or sound transducer), the transmission properties of the room, and speech intelligibility for the listener.

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DIN 18041:2004-05

3.4 speech intelligibility basic criterion for acoustic quality in rooms for spoken presentation. To ascertain the subjective speech intelligibility, the percentage of correctly identified syllables, words or sentences can be determined. Objective measurement methods make use of physical parameters of the spoken communication in the room (e.g. speech level, sound propagation, and background noise) 3.5 background noise if not otherwise specified, background noise is determined in accordance with DIN 45641 as the A-weighted equivalent continuous sound pressure level over the time that is representative for the disturbance

NOTE

The A-weighted total noise pressure level, LNA, is expressed in decibels.

3.5.2 noise pressure level of building-generated noise LNA,Bau sound pressure level in the room concerned that is generated by external noise, noise from neighbouring rooms, from building services equipment, sanitary facilities and permanently installed media technical equipment NOTE 1

The A-weighted noise pressure level, LNA,Bau, is expressed in decibels.

NOTE 2 For individual noise components, such as noise generated by building services equipment, there are other descriptive parameters, such as the maximum A-weighted sound pressure level, LAF, max, expressed in decibels.

3.5.3 noise pressure level of noise generated by room equipment LNA,Betrieb sound pressure level of additional equipment operated in the room concerned, such as mobile equipment for the reproduction of images and sound, etc. NOTE 1 This can generally be calculated from the A-weighted sound power level, LWA, of the equipment operated in the room, in accordance with VDI 3760. NOTE 2

LNA,Betrieb is expressed in decibels.

NOTE 3 To guarantee comparability of results, the relevant measurement standard should be cited when giving sound power levels of equipment; e.g. A-weighted sound power level LWA = 67 dB, measured in accordance with DIN EN ISO 3746, or of projectors, measured in accordance with DIN 45635-60 or ISO 10996.

3.5.4 noise pressure level of noise generated by the public LNA, Publ noise generated by the public (here: presenters, students, listeners, users of the room), such as the scraping of chairs, murmuring, whispering, coughing, movement noise, etc. NOTE

The A-weighted noise pressure level of the noise generated by the public is expressed in decibels.

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3.5.1 total noise pressure level LNA sound pressure level that contains all noise components affecting the listener during use, such as noise generated by building systems, operating equipment or the public, and which is determined at ear height for the area in which people are normally located

DIN 18041:2004-05

3.6 sound absorption removal of sound energy from a room or area of the room by conversion into another form of energy (e.g. heat: “dissipation”) or exit of the sound from the area under consideration (“transmission”) 3.7 sound absorption coefficient

α

ratio of the sound energy that is not reflected from a surface to the incident sound energy In the case of complete sound reflection α = 0; in the case of complete sound absorption α = 1.

NOTE 1

NOTE 2 The sound absorption coefficient of a material, αS, is determined for diffuse sound incidence by means of acoustic testing in a reverberation room (DIN EN 20354).

3.8 practical sound absorption coefficient

αp

sound absorption coefficient for an octave band, calculated in accordance with DIN EN ISO 11654 using results obtained in measurements in accordance with DIN EN 20354 3.9 weighted sound absorption coefficient

αw

single number value for the sound absorption of a material, which is calculated by comparing practical sound absorption coefficients (see 3.8) with the values in the reference curve specified in DIN EN ISO 11654 3.10 spatially averaged sound absorption coefficient

α

sound absorption coefficient averaged over the total room surface and calculated as follows: n

α =

∑ α i × Si i =1

(1)

S

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where

αi

is the sound absorption coefficient for partial surface, Si and

S

is the sum of all partial surfaces, Si.

3.11 equivalent sound absorption area A imaginary area with complete sound absorption (α = 1) which would absorb the same proportion of sound energy as the whole surface area of a material, a room, or objects and people The equivalent sound absorption area, A, of a room can be calculated from the partial surfaces, Si, with known sound absorption coefficients, αi, and the sound absorption of the objects or people inside the room, using equation (2): A=

n

∑

α i × Si +

i =1

k

∑ A j + 4 × mV

(2)

j =1

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DIN 18041:2004-05

where

αi

is the sound absorption coefficient of partial surface, Si;

Aj

is the equivalent sound absorption area of non-planar materials, objects (e.g. chairs) and people within the room, in m2;

m

is the attenuation coefficient in air in accordance with DIN EN 12354-6:2002-03, Tab. 1, in m–1;

V

is the total room volume, in m3.

The equivalent sound absorption area of a room can also be determined on the basis of the reverberation time, approximated using equation (3): A = 0,163 ×

V T

(3)

where V

is the total room volume, in m3;

T

is the reverberation time, in s;

A

is the equivalent sound absorption area, in m2.

3.12 reverberation totality of the reflected sound that is still present in a closed room after the sound source has ceased making sound NOTE

The decay of the sound pressure level can be objectively described by the reverberation time, T.

3.13 reverberation time T time it takes for the sound pressure level in a room to decay by 60 dB once sound excitation has ceased NOTE This time begins with the end of the excited state. The reverberation time can be determined by carrying out measurements in existing rooms in accordance with DIN EN ISO 3382. Calculating the reverberation time on the basis of the reverberation theory (using the Sabine model) is primarily appropriate for rooms with an approximately diffuse sound field and whose length and width are between 0,3 to three times the height of the room, where the length is at most twice the room width. For shallow rooms (length > five times the height, width > three times the height) or long rooms (length > five times the height, width = 0,3 to three times the height), rooms with complicated primary shapes (circular or elliptical ground plans, concave curved cut-outs, coupled room spaces, etc.) and an uneven distribution of sound absorption areas, the actual reverberation times can deviate from values obtained using equation (4). T = 0,163 ×

V A

(4)

where V

is the total room volume, in m3;

T

is the reverberation time, in s;

A

is the equivalent sound absorption area, in m2.

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DIN 18041:2004-05

3.14 hearing loss/hearing impairment hearing loss verifiable by means of tone audiometric testing and which occurs primarily at frequencies above 1 kHz. Hearing impairment is any hearing loss that leads to a reduction of hearing ability in comparison to a person with good hearing NOTE Hearing loss/hearing impairment are accompanied by a significantly reduced speech comprehension under noisy conditions, often with a narrowing of the usable dynamic range (recruitment). In particular the high-frequency components of the sibilant and explosive sounds that are important for speech intelligibility are no longer perceived, or are perceived only in a severely weakened form (see also VDI 2058 Part 2).

4 4.1

Requirements for acoustic quality over medium and large distances (group A rooms) General

Depending on use, good acoustic quality in group A rooms is influenced by design aspects, ambient comfort, and the acoustic interaction between room geometry, size and furnishings, in addition to the total noise pressure level. Group A rooms include —

conference rooms, courtrooms, council chambers and function rooms;

—

classrooms, seminar rooms, lecture theatres;

—

convention rooms and interaction rooms;

—

group rooms in nursery schools and children’s day care centres, senior day care centres;

—

community rooms;

—

sports halls and swimming baths.

If use is to be primarily in the area of spoken communication, there are three components to consider: —

speaker,

—

transmission, and

—

hearing/understanding

which are influenced by sound reflection, reverberation and background noise. For optimally functioning spoken communication over medium and large distances with low or moderate effort by the speaker (normal to raised speech), as much direct sound and clarity-enhancing initial reflections (up to 30.. 50 ms) as possible are to be directed from the speaker to the listener. Therefore, long-lasting reverberations, time-delayed reflections with high energy levels, and background noise are to be considerably reduced [2]. Sound systems can be helpful in some cases. In multi-purpose rooms, a compromise between the differing acoustic requirements and other parameters shall be striven for, giving priority to value and/or predominant function, depending on the status of the room. It shall be possible for people with impaired hearing to participate in spoken communication. For this purpose more stringent building and acoustic requirements are to be set.

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People who still have a certain level of hearing ability will be able to participate in communication to a limited extent if the room is equipped with suitable technical aids (hearing aids, inductive loops, infrared or radio transmission). Compensation shall be made for people whose hearing ability is severely limited or non-existent by using visual means (sign language, lip reading or text reading).

4.2

Building acoustics requirements

4.2.1

Background noise

4.2.1.1

Permissible total noise pressure level

To achieve a largely unhindered speech intelligibility, the A-weighted speech sound pressure level, LSA, shall be significantly higher than the total noise pressure level, LNA. 4.2.1.2

Permissible noise pressure level of building-generated noise

Table 1 gives the permissible total noise pressure levels for building-generated noise, LNA, Bau, which should not be exceeded. Table 1 — Noise pressure level of building-generated noise as a function of room use Column

1

2

3

Acoustic requirements for room based on use

Noise pressure level of the buildinggenerated noise LNA,Bau dB

Suitabilitya for a speaker/ listener distance that is

Line

4

5 Suitabilitya for the comprehension of difficult or foreign language texts

averagebc

largeb

Suitabilitya for people with hearing loss

1

I (minimum)

≤ 40

+

–

–

–

2

II (average)

≤ 35

+

o

o

o

3

III (high)

≤ 30

+

+

+

+

a

“+” suitable, “o” suitable under certain conditions, “–” not suitable

b

For an average distance between speaker and listener, a separation of 5 m to 8 m can normally be assumed, for larger distances > 8 m.

c

Also suitable for a smaller distance between speaker and listener, i.e. up to about 5 m.

In rooms in which people with impaired hearing are to understand each other, and/or people are to speak or understand a foreign language (VDI 2058 Part 3), the noise pressure level of building-generated noise shall be as in table 1, line 3, column 2. 4.2.1.3

Permissible noise pressure level of noise generated by equipment

The noise pressure level of noise generated by operating equipment measured at the closest listener location should not exceed the values specified in table 1, column 2. 4.2.1.4

Permissible noise pressure level of the noise generated by the public

As a rule, noise generated by the public should not exceed the values given in table 1, column 2. However, since it is not possible to directly influence the level of such noise, special measures shall be taken (see 5.1.2).

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4.2.2

Structural noise control

Mandatory requirements for sound insulation are specified in DIN 4109:1989-11. The requirements listed there in table 3, lines 38 to 45 for sound insulation in schools and similar educational buildings shall be used by analogy as guidelines for sound insulation between neighbouring rooms for spoken communication. In music schools or similar institutions, the values for airborne sound insulation required to protect teaching and rehearsal rooms against noise from other rooms and from horizontally adjacent halls and corridors shall be 3 dB to 5 dB greater than those specified in DIN 4109:1989-11, table 3, lines 40 and 44 for “very noisy rooms”. Where there are sound systems, the potential for disturbance generally increases as regards neighbouring rooms. In this case, such rooms are to be considered as requiring increased sound insulation protection. The requirements for sound insulation between “very noisy rooms”, such as kitchens or rooms with building service equipment, and rooms for spoken communication (“noise sensitive rooms”) are specified in table 5 of DIN 4109:1989-11. Requirements for protection against external noise are given in DIN 4109:1989-11, table 8, column 4 (“rooms in dwellings ... class rooms, etc.”). The air-borne and structure-borne sound insulation between plant rooms and rooms for spoken communication is to be designed so that the maximum permissible A-weighted sound pressure level, LAF,max, is maintained at ≤ 30 dB, measured in accordance with DIN 52219. For this purpose, the requirements specified in table 5 of DIN 4109:1989-11 are generally sufficient.

4.3 4.3.1

Room acoustics parameters Volume index

In order to achieve a reverberation time that is suitable for the use of the room, the volume index k (room volume per place) should be as shown in table 2. When these values are exceeded, more extensive sound absorption measures may be required; this will reduce the sound pressure level of the sound sources at the listener’s location, however. If the values are lower (this is to be justified), the required reverberation time is not guaranteed. Table 2 — Volume indices as a function of room use 1

2

Primary use of the room for

Volume index, k, in m3/place

1

spoken presentations

3 to 6

2

music and spoken presentations

5 to 8

3

music presentations

7 to 12

Column Line

4.3.2

Reverberation time

The target value for the reverberation time at average frequencies (Tsoll) is to be taken from figure 1, depending upon the mode of use and an effective room volume V between 30 m3 and 5 000 m3 (in the case of sports halls and swimming baths without public present, up to 8 500 m3). The curves “music”, “speech” and “teaching” refer to occupied rooms.

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The curves in figure 1 refer to the following modes of use: Music: —

music teaching rooms with live playing of music and singing;

—

council chambers, function rooms for musical presentations.

Speech: —

courtrooms, council chambers;

—

church halls, assembly rooms;

—

music rehearsal rooms in music schools, or similar rooms;

—

sports halls or swimming baths with public present.

Teaching: —

teaching rooms (apart from music rooms);

—

music teaching rooms with audiovisual presentation;

—

group rooms in nursery schools and nursery day care centres, senior day care centres;

—

seminar rooms, interaction rooms;

—

lecture theatres;

—

rooms for tele-teaching;

—

convention rooms, conference rooms;

—

presentation rooms exclusively for electro-acoustic use.

Sport 1: —

sports halls and swimming baths without public present, for normal use and/or single teaching activity (one class or sports group, single source of communication content).

Sport 2: —

sports halls and swimming baths without public present, for normal use and/or multiple teaching activities (several classes or sports groups with various sources of communication content).

Comparable rooms are to be classified by analogy. In figure 1 a dashed line represents room volumes which are atypical for the rooms covered by this standard, while a dot-dash line identifies room volumes greater than those within the scope of the standard. In the case of multipurpose rooms as in line 2 of table 2, intermediate values between the relevant curves in figure 1 are to be determined, taking the value for the main mode of use into consideration. The target reverberation times are given as a function of frequency in figure 2 for speech and figure 3 for music. Guideline values (reference values) for frequencies below 100 Hz and above 5 000 Hz are shown in these two figures as dashed lines.

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DIN 18041:2004-05

In sports halls and swimming baths without public present the Tsoll value taken from figure 1 is to be maintained between 250 Hz and 2 000 Hz with an accuracy of ± 20 %. NOTE value.

In general, the reverberation time of an unoccupied room should not lie more than 0,2 s above the required

Figure 1 — Target value, Tsoll, for the reverberation time for different modes of use

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Music:

V ⎛ ⎞ Tsoll = ⎜ 0,45 lg 3 + 0,07 ⎟ s m ⎝ ⎠

(5)

Speech:

V ⎛ ⎞ Tsoll = ⎜ 0,37 lg − 0,14 ⎟ s 3 m ⎝ ⎠

(6)

Teaching:

V ⎛ ⎞ Tsoll = ⎜ 0,32 lg − 0,17 ⎟ s 3 m ⎝ ⎠

(7)

Sport 1:

V ⎛ ⎞ Tsoll = ⎜1,27 lg − 2,49 ⎟ s 3 m ⎝ ⎠

(8)

Sport 2:

for 2 000 m3 ≤ V ≤ 8 500 m3.

V ⎛ ⎞ Tsoll = ⎜ 0,95 lg − 1,74 ⎟ s 3 m ⎝ ⎠

(9)

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Figure 2 — Target range for reverberation time, as a function of frequency, for speech

Figure 3 — Target range for reverberation time, as a function of frequency, for music

For people with impaired hearing, shorter reverberation times are perceived as being acoustically more favourable for spoken communication. The current opinion among experts in accessible planning and building is that rooms used by persons with impaired hearing should — for the octave bands from 250 Hz to 2 000 Hz — have target reverberation times which are up to 20 % lower than those specified in figure 1, particularly in rooms intended for spoken communication and teaching and having a volume up to 250 m3; figure 2 should not be used for this frequency range. Similar requirements apply for communication in a foreign language, for communication with people who speak German as a foreign language, and for communication with people who for other reasons require increased speech intelligibility, e.g. people with speech or speech processing problems, concentration or attention problems, or general learning difficulties.

4.4

Room geometry

The primary structure of the room should avoid circular or elliptical ground plans if additional measures to improve acoustics are not taken. Trapezoidal ground plans with side walls converging in the direction of presentation are to be given preference over ground plans with diverging walls. Concave curved wall and ceiling surfaces are acoustically significant and — where additional sound insulation measures are not taken — are therefore to be avoided if the radius of curvature lies between half and twice the distance between the presenter/listener and the largest distance to the curved surface (e.g. room height in the case of curved ceilings). Balconies, raised arcades, galleries and tiers should be located above the underlying spectator level with a clear height, H, of at least half or the same value as the depth of the space above, L:

H ≥ (0,5 to 1,0) L

(10)

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For a sufficiently direct sound projection without changes in timbre, the seating should be elevated, as a longitudinal profile of the listener surface area with a visual field angle of at least 12° in the form of a logarithmic spiral. If there are some areas in which the seating level is constant, there is to be a polygonal matching to the spiral. When a level layout is necessary, selecting an appropriate basic height or staggering the presentation area (stage platform, podium) can be an acceptable compromise, acoustically and optically. Figure 4 gives recommended values for seating elevation as a function of distance to the sound source, for podium heights of 0,6 m, 0,8 m, and 1,0 m, where the head-height of the speaker/singer at the front of the presentation zone (podium) is normal.

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Figure 4 — Seating elevation for a visual field angle of 12° NOTE People with impaired hearing rely on additional optical information (lip movements, gestures, mime, writing). This is to be taken into account when selecting the speaker location, its lighting and the technical equipment in the room.

The secondary structure of the room (configuration of the walls and ceiling) is to be designed for sound deflection and scattering, on the basis of the room geometry. —

Where the predominant room use is for spoken communication, the path difference between the direct sound (along the line of sight to the sound source) and the energy-rich reflected sound component (e.g. first sound reflection from the wall and/or ceiling) should not be greater than 17 m. If in this case the distance between the wall surfaces behind the presentation area and those opposite to it is greater than 9 m, then the rear wall is to be acoustically treated (see 5.2).

—

Taking into account the permissible path difference, initial sound reflections which increase distinctness and clarity are to be achieved by means of sound reflecting central ceiling areas, and in the case of musical use, by means of additional mobile wall panels in the presentation zone, if the existing boundary surfaces make the room unsuitable for this use due to the greater distances involved.

Parallel surfaces without additional acoustic treatment (e.g. treatments to improve sound absorption or diffuse scattering, or inclining surfaces by at least 5°) should be avoided.

The boundary surfaces of the presentation zone are to be sound-reflecting. If the room is used exclusively for spoken communication, these surfaces should be configured as low frequency sound absorbers, even when electro-acoustic sound equipment is used.

4.5 4.5.1

Electro-acoustic sound systems for spoken presentations Selection criteria

General criteria are given below which should help planners estimate whether a sound system will be necessary in rooms as in this standard which are used for general spoken communication without audiovisual equipment. It is assumed that the requirements of 4.2 to 4.4 have been met. An electro-acoustic sound system cannot compensate for inadequately designed room acoustics.

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—

The electro-acoustic amplification of speech is not generally necessary in rooms up to about 250 m3 in volume.

—

The necessity for an electro-acoustic sound system in larger rooms is determined primarily by the speech level (see Annex D) and the total noise pressure level (see 4.2.1). When room volumes are greater than those specified in table 3 for various noise pressure levels, a sound system is required for normal to raised speech levels. Table 3 — Room volume, which when exceeded means that an electro-acoustic sound system is required for normal to raised speech levels, as a function of the noise pressure level of building-generated noise according to 4.2.1.2

Column

1

2

A-weighted noise pressure level from table 1, column 2 dB

Room volume

1

40

500

2

35

1 000

3

30

2 000

Line

—

m3

In doubtful cases (unfavourable room shapes, cantilevered balconies and galleries, shallow rooms, usage with unpractised speakers) where the room volume is greater than 250 m3, electro-acoustic equipment should be allowed for at the design stage with a view to installation at a later date (laying of ductwork, cable conduits, location of loudspeaker mountings, etc.). After the building has been completed, word and syllable intelligibility tests can be used to determine the necessity for any retrospective installation.

The values for various parameters given in table 4 are to be achieved in rooms which meet the requirements of 4.2 to 4.4. Table 4 — Required values for various parameters when an electro-acoustic sound system is used (see Annex A)

Column

1

2

Room type

Clarity index

Line

3

4

5

C50

Common Intelligibility Scale CIS

Speech Transmission Index STI

Articulation Loss of Consonants Alcons

1

Small auditorium, lecture theatre, classroom

≥ 0 dB

≥ 0,75

≥ 0,56

< 8%

2

Sports hall or swimming bath, with public present

≥ –2 dB

≥ 0,70

≥ 0,50

< 12%

16

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NOTE Certain speaker-listener situations can also justify the introduction of a sound system, even in relatively small rooms (e.g. medical investigation in the lecture theatre of a university clinic with doctor-patient discussion and a larger number of listeners).

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4.5.2

Direct sound amplification by means of electro-acoustic sound systems

In large rooms, particularly rooms that are long and/or shallow, the sound pressure level at the listener location is often not high enough to achieve an acceptable level of speech intelligibility. In such cases electro-acoustic sound systems are needed to amplify sound. Here microphones are used to receive the acoustic signal, which is amplified and radiated back into the same room via loudspeakers. Such sound systems are used to increase speech intelligibility in the area where the public is present. This cannot generally be achieved by simply increasing the volume of the speech signal, because in this case sound reflections that reduce intelligibility are amplified at the same time. Therefore, when selecting the sound transducer it should be ensured that there is sufficient directionality in the relevant frequency range so that a high direct sound component is achieved. In this way the maximum possible loop amplification is also increased, despite the fact that the microphone and the loudspeaker are located in the same room. For sound systems for spoken presentations, a restricted frequency range with small low frequency sound signal components can be used, since these components do not contribute to speech clarity. For sound source recognition, however, attention is to be paid to achieving as natural a timbre of the signal transmission as possible. To increase the listeners’ concentration, the acoustic directional reference to the speaker location is to be ensured. Here deviations in the horizontal plane are subjectively perceived as being more disturbing than deviations in the vertical plane. Sound systems for speech differ greatly from music sound systems. In many cases the two tasks cannot be carried out with the same types and arrangements of loudspeakers. In any event, the settings of the system are to be suited to the specific requirements for speech and music. When decentralized sound systems are used, the resulting subjectively greater reverberance is to be taken into account. 4.5.3

Announcement systems, alarm systems

In the case of announcement systems and alarm systems, the speaker’s microphone and loudspeakers are as a rule in different rooms. In this way there is no risk of electro-acoustic feedback. Since no uniformity between optical and acoustic directional reference is required, decentralized loudspeaker systems with a low sound power output from each of the individual sound emitters can normally be used. Here too care should be taken that the direct sound component is high and the diffuse sound component is low in the listener plane. In the case of announcement systems that also serve to provide an alarm, the danger signals are to be distinctly audible and visually perceivable (using acoustic and optic signals simultaneously, see DIN EN 457 and DIN EN 60849 (VDE 0828-1)). 4.5.4

Sound systems for the hearing impaired

The hearing impaired require a significantly higher direct sound component with correspondingly reduced diffuse sound and noise components in comparison to those with good hearing (more favourable LSA – LNA separation) and therefore the usual sound systems with loudspeakers are generally not sufficient. Rather, the acoustic signals need to be supplied directly to each person. For this purpose special systems are to be installed in parallel to the normal speech sound systems (see Annex C). Under certain circumstances such a system is also to be available in rooms in which no sound system is required for people with good hearing.

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5

Measures to ensure high acoustic quality over medium and larger distances (group A rooms)

5.1

General measures

5.1.1

Spatial arrangement of rooms

When designing rooms for spoken communication, care should be taken that rooms with a low noise potential are located next to each other, in addition to taking the functional interdependence of the rooms into consideration. Maintaining a large distance from main traffic routes inside and outside the building, as well as from loud function rooms and plant rooms will also reduce the need for noise control. 5.1.2

Noise in the room that is being used

The noise generated by operating equipment (see 3.5.3) is to be such that the noise measured at the closest listener location meets the requirements of table 1. If this is not the case, quieter equipment is to be selected, or additional measures such as sound-insulating enclosures or acoustic screens are to be used. In order to keep the noise generated by the public as low as possible, carpeted floors and floor structures with a high internal damping etc. should be used. Noise caused by contact of movable furniture (tables, chairs) with the floor shall be reduced by suitable means (e.g. rubber underlays, felt gliders, etc.).

5.2

Specific design measures

5.2.1

Small rooms with volumes up to about 250 m3

5.2.1.1

Room geometry

The design measures described here apply particularly to meeting rooms and classrooms, group rooms in nursery schools and children’s day care centres and other rooms that primarily serve for spoken communication, even when audiovisual media are being used. Because of the room dimensions, over-damping as a result of the sound-absorbing measures taken is not generally to be expected. For small rooms, higher volume indices than those shown in table 2 are advantageous if suitable measures are taken. In small rooms particularly, disturbing droning or booming effects can occur at low frequencies. These can be counteracted by means of sound absorbing measures and/or the selection of suitable room proportions, see e.g. [6]. 5.2.1.2 5.2.1.2.1

Sound absorptive surfaces Calculations based on the reverberation theory

The type and extent of the sound absorptive surfaces to be installed depend upon the room volume and the acoustic properties of such surfaces, including the objects used to furnish the room. For room volumes up to about 250 m3 it is in general sufficient to have a room design taking into account the octave band centre frequency range between 125 Hz and 4 000 Hz and/or third octave band centre frequencies between 100 Hz and 5 000 Hz, disregarding the sound attenuation in the air as in 3.11. The required absorption coefficient, αS, may be taken from test reports as in DIN EN 20354. Guideline αS values are listed in Annex B of this standard. 5.2.1.2.2

Simplified estimation for the teaching mode of usage

For small rooms used for teaching (see 4.3.2) a simplified estimate of the sound absorptive surfaces required can be made. Here it is assumed that the rooms have furnishings that are to a large extent sound reflecting.

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For this purpose, table 5 gives guideline values for the required equivalent sound absorption surface area, Aerf, and the required surface area for different weighted sound absorption coefficients, αw. It is recommended that a frequency-dependent calculation of the reverberation time to be expected in the finished room be carried out in accordance with 5.2.1.2.1. Table 5 — Guideline values for estimating the required sound absorption surface area as a function of αw, for rooms used in the teaching mode, with a volume up to 250 m3

Column

1

Line

2

3

4

5

6

7

1

Room volume in m3

30

70

100

150

200

250

2

Required (additional) equivalent sound absorption surface area, Aerf, in rooms having low sound absorbing furnishings, i.e. non-upholstered seating, with little or no sound absorbing floor covering (linoleum, needled felt), in m2

10

14

17

24

31

34

3

Guideline value for the required surface area Si ± 20 % for a selected weighted sound absorption coefficient, αw, as in DIN EN ISO 11654

5.2.1.2.3

Si

Aerf

αw

Distribution of sound absorptive surfaces

As a rule, the absorptive surfaces should be distributed evenly throughout the room. The arrangements shown in figures 5b and 5c are suitable. The size of the surface is to be based on calculations as in 5.2.1.2.1 or estimated as in table 5. Sound absorbers which are primarily effective in the low frequency range are particularly effective near the sound source, and in room corners or angles. If the room has a rectangular ground plan and the walls are plane and not interrupted by furniture, shelving, window recesses or objects such as large notice boards and pin boards, there is a risk that flutter echoes may occur where there is a completely sound absorptive covered ceiling. This can be avoided if a central area of the ceiling is sound reflecting as shown in figures 5b and 5c. However, the walls are to be partially sound absorptive, as compensation. Since there is no risk of over-attenuation in rooms with a volume up to about 250 m3, a ceiling with a fully sound absorptive surface can be used in combination with a similarly sound absorptive rear wall. NOTE 1 As a rule, textile floor coverings absorb sound only at high frequencies and are not sufficient as the sole measure to improve room acoustics. NOTE 2 The sound absorption of curtains or other internal means of darkening the room is strongly dependent on their arrangement, the material selected and their effective surface area.

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Figure 5 — Distribution of sound absorptive surfaces in small to medium-size rooms, e.g. teaching and meeting rooms (above: side elevations, below: views of the undersurface of the ceiling) 5.2.2

Medium-sized rooms and small halls with volumes from about 250 m3 to 5 000 m3

5.2.2.1

Room/hall geometry

Such rooms are usually large classrooms, seminar rooms or lecture theatres. Because of the room size, it is not only necessary to have the correct arrangement of sound absorptive materials suitable for the relevant frequencies, but also to ensure that useful reflections are deflected and delayed so that harmful reflections are avoided. The volume index should lie in the range specified in table 2. Rooms that are very low compared with their length and/or width should be avoided. The proportions of larger rooms are less critical even at low frequencies because of the higher density of natural frequencies. Wall surfaces that are parallel to each other and untreated are just as unfavourable as concave curved or angled surfaces, which in areas occupied by people (or, possibly, microphone positions) can lead to flutter echoes or focusing of the sound. In larger auditoria, elevated seating is to be given preference over a flat seating arrangement; it is advantageous if the speaker position is raised above the seating level (e.g. platform, podium stage); for more details see 4.4. 5.2.2.2 5.2.2.2.1

Sound absorptive surfaces Calculations based on the reverberation theory

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The required sound absorptive surface areas can be calculated for the relevant third-octave or octave band centre frequency ranges as in 3.11. The required sound absorption coefficient, αS, and the equivalent sound absorption area, A, may be taken from test reports as in DIN EN 20354. Guideline αS values are listed in Annex B of this standard. In existing rooms in which acoustic improvements are required, the actual reverberation times should be measured in accordance with DIN EN ISO 3382 as the basis for planning. Such measurements can also be used for checking the effectiveness of the measures carried out. 5.2.2.2.2

Distribution of sound absorptive surfaces

In rooms with a length of more than about 9 m, time-delayed sound components can be deflected from the rear wall into the front area of the room, either directly or via angle reflections. This leads to a reduction in the level of speech intelligibility (see figure 6a). In this case the sound reflecting surfaces shall either be covered

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with a sound absorptive material, or inclined so that the impinging sound is reflected as a beneficial amplification towards the listeners who are most distant from the sound source (see figures 6b and 6c). Sectioning of surfaces is also beneficial.

Figure 6 — Rear wall reflections

In the case of parallel surfaces (see figure 7a) at least one of the opposing surfaces should be sound absorptive or sectioned (figures 7b and 7c). This applies particularly in the case of larger rooms that do not have tiered seating. An inclination of the surfaces by at least 5° is also favourable.

Figure 7 — Parallel walls

A suitable arrangement and alignment of reflecting surface areas is needed to amplify beneficial sound at larger distances, thus improving speech intelligibility. The wall behind the speaker should be sound absorptive at low frequencies. The central part of the ceiling, from which the first reflections reach listeners, should be sound-reflecting in the medium and high frequency ranges, and configured as a low frequency sound absorber. If the ceiling or the side wall surfaces are not plane, but are broken up into large areas, then the individual elements are to be aligned so that sound is directed to the central and rear areas of the auditorium (see figure 8).

Figure 8 — Beneficial reflections for the rear area of the auditorium (a and b: side elevations; c: ground plan)

In rectangular rooms with largely plane surfaces (e.g. sports halls and swimming baths), with sound absorptive surfaces distributed on one surface only (e.g. only the ceiling has a sound absorbent covering), significantly longer reverberation times than those calculated using the equation in 3.11 can occur. To prevent this, combinations of sound absorbing or sound scattering measures should be used on at least one wall surface. In doubtful cases, more precise prognoses can be made by using more refined static analysis methods (simulation methods using mathematical or physical models). This assumes the use of suitable room acoustics simulation software, and experience, and an ability to work reliably with these tools.

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5.2.3

Special cases

In small music rehearsal rooms and practice rooms a textile floor covering can provide the required sound absorbance in the high frequency range. In larger rehearsal rooms, the central section of the ceiling is to be sound reflecting and shall not be aligned parallel to the reflecting floor (angle of inclination at least 5°). As a rule, good room acoustics for various rehearsal situations should be promoted by using movable sound-absorbing curtains hung on two adjacent walls.

6 6.1

Recommendations and measures to ensure acoustic quality in rooms over smaller distances (group B rooms) General

In contrast to the requirements in clause 4, the recommendations given here enable spoken communication over small distances in group B rooms; these recommendations focus on increasing sound absorption and reducing the total noise pressure level and reverberation times. However, maintaining the target value for the reverberation time is not necessary to meet the objectives of this clause.

—

sales rooms, eating places;

—

public areas for short-distance and long-distance public transport, ticket halls and banking halls;

—

consulting rooms in solicitors’ and doctors’ practices, individual offices;

—

multiple-occupancy and open-plan offices;

—

municipal public offices;

—

operating theatres, treatment and rehabilitation rooms, sick rooms

—

reading rooms and lending counters in libraries;

—

workrooms (e.g. training workshops);

—

public areas;

—

foyers, exhibition rooms, stairwells.

6.2

Measures

Basic measures to reduce the total sound pressure level are to be taken as in 5.1 by analogy. In particular the reduction of noise generation is necessary (including noise generated by the public, equipment operating in the room, and building services systems) (see DIN EN ISO 11690-1 and DIN EN ISO 11690-2). Increasing sound absorption reduces the total noise pressure level and reverberation times. Sound absorptive planar materials, or furnishings can be used for this purpose. Sound absorbers are to be introduced if 1.

by so doing the sound pressure level is reduced by at least 3 dB. Here the existing equivalent sound absorption area is to be at least doubled, for the octave bands determining the sound pressure level.

2.

it is expected that sound insulation measures will result in a spatially averaged sound absorption coefficient, α (see 3.10) no greater than 0,35 between octave band centre frequencies of 250 Hz to

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Group B rooms include:

DIN 18041:2004-05

2 000 Hz. While greater sound absorption is indeed beneficial, the feasibility of the necessary technical measures and related costs are to be considered. NOTE 1 The expected reduction in sound pressure level, ΔL, can be approximated for the relevant octave bands using equation (11): ⎛ A + ΔA ⎞ ⎟ dB ΔL = ⎜⎜10 lg 1 A1 ⎟⎠ ⎝

(11)

where ΔL

is the difference between the sound pressure level in the untreated room and that in the room provided with the additional equivalent sound absorption area, ΔA, in the diffuse sound field (for rooms as in this standard), in dB;

A1

is the equivalent sound absorption area of the untreated room, in m2;

ΔA

is the proposed additional equivalent sound absorption area, in m2.

The graphical representation of equation (11) is shown in figure 9:

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The equivalent sound absorption area is to be calculated as in 3.11, equation (2). Values for αi and Aj are to be taken from the literature; examples of values for αi are given in Annex B.

Figure 9 — Relationship between the reduction in sound pressure level, ΔL, in the diffuse sound field and the additional equivalent sound absorption area, ΔA, for equivalent sound absorption surface areas, A1, of the untreated room

Guideline values for additional sound absorbing areas needed to ensure these recommendations are fulfilled are given in table 6.

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Table 6 — Guideline values for the free ceiling and wall surface areas to be covered with sound absorbers, as a multiple of the room floor area, for an average clearance height of 2,5 m, when using sound absorbers in various types of rooms Column

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Weighted sound absorption coefficient

αw

Room type

1,00 0,95 0,90 0,85 0,80 0,75 0,70 0,65 0,60 0,55 0,50 0,45 0,40 0,35 0,30 0,25 0,20

Line 1

Sales rooms, work rooms, call centres, read- 0,9 ing rooms in libraries

0,9

1,0

1,1

1,1

1,2

1,3

1,4

1,5

1,6

1,8

2,0

—

—

—

—

—

2

Multiple occupancy or open plan offices with office machinery, booking halls, municipal public 0,7 offices, operating theatres, sick rooms, lending counters in libraries, public lending libraries

0,7

0,8

0,8

0,9

0,9

1,0

1,1

1,2

1,3

1,4

1,6

1,8

2,0

—

—

—

3

Individual offices, consultation rooms, treatment and rehabilitation rooms, break halls, eating places, dining halls, canteens with a floor area greater than 50 m2

0,5

0,5

0,6

0,6

0,6

0,7

0,7

0,8

0,8

0,9

1,0

1,1

1,3

1,4

1,7

2,0

—

4

Stairwells, foyers, exhibition rooms, traffic areas (halls, corridors and 0,2 ante-rooms) with high levels of foot traffic and public areas for local public transport

0,2

0,2

0,2

0,3

0,3

0,3

0,3

0,3

0,4

0,4

0,4

0,5

0,6

0,7

0,8

1,0

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The table is to be used for comparable rooms by analogy. NOTE 2 In rooms in which there are many people, a significant part of the noise level is generated by the people themselves. This is especially true in eating places, train stations, etc. In this case higher level reductions than those calculated using equation (11) are to be expected, since the speech volume decreases with decreasing noise pressure level, as a rule. NOTE 3 Experience shows that low-pile floor coverings, conventional upholstered furniture, blinds and curtains are not well suited as effective reverberation time reduction. Soft floor coverings, however (e.g. rugs, fitted carpeting), prevent noise generation and therefore contribute significantly to the reduction of the total noise pressure level. NOTE 4 If low-frequency noise is not to be expected in the room under consideration, the recommended spatially averaged sound absorption coefficient at 250 Hz is only of secondary importance (e.g. in stairwells, halls and corridors). NOTE 5 In normally furnished rooms without additional sound absorbing measures, a spatially averaged sound absorption coefficient, α , of 0,10 to 0,20 can be expected, depending on the extent of the furnishings. Where α = 0,35, the total noise pressure level in the diffuse field can be reduced by about 3 dB to 6 dB, and the reverberation time can be reduced by a factor of 1,8 to 3,5, as compared with the untreated room.

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Annex A (informative) Terms relating to speech intelligibility

A.1 Clarity index, C50, for speech (“early-to-late index” as in DIN EN ISO 3382) The parameter C50 (termed the “early-to-late index” in DIN EN ISO 3382) describes the intelligibility of speech or singing. It is calculated as 10 times the logarithm of the ratio of the sound energy impinging at the listener location up to a delay time of 50 ms after impingement of the direct sound, to the sound energy impinging at a later time: ∞ ⎛ 0,05s ⎞ ⎜ ⎟ C50 = 10 lg⎜ p 2 (t ) dt / p 2 (t ) dt ⎟ dB ⎜ 0 ⎟ 0,05 s ⎝ ⎠

∫

∫

(A.1)

where is the instantaneous sound pressure level of the impulse response.

p(t)

Here the source for the sound field excitation should exhibit the directional characteristic of a speaker or singer to ensure comparability with speech intelligibility limiting values or reference values. When evaluating electro-acoustic sound systems, the relevant sound transducer shall be used as the source. In general, good speech intelligibility is ensured if C50 ≥ 0 dB. The limit for low discernment of differences in clarity lies at ± 2,5 dB. An equivalent criterion is the definition (also called “Deutlichkeit” in English) D, also designated as D50, which is calculated from the ratio of the sound energy impinging at the listener location up to a delay time of 50 ms after impingement of the direct sound, to the sound energy impinging later (it can also be expressed as a percentage): ∞

0,05 s

D=

∫

∫

p 2 (t ) dt / p 2 (t ) dt =

0

0

1 1+ 10

−

(A.2)

C50 10 dB

where p(t)

is the instantaneous sound pressure level of the impulse response, and

C50

is the clarity index according to equation (A.1).

A.2 Speech Transmission Index, STI The determination of STI values is based on the measurement of the reduction of the signal modulation between the location of the sound source and the listener at octave central frequencies from 125 Hz to 8 000 Hz. Speech intelligibility is not only reduced by reverberation and disturbing noise, but in general by all extraneous signals or signal modifications that occur along the path between the source and listener location.

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For a syllable intelligibility of at least 85 % the target figure for D should be ≥ 0,5 or 50 %.

DIN 18041:2004-05

The STI can be determined directly by measuring the modulation transfer functions in the corresponding octave bands, or on the basis of the room impulse response. Changes in the STI of as little as 0,03 can be discerned [5]. To reduce the resource requirement for measurements, an abbreviated rapid method was defined with a corresponding index, RASTI (Rapid Speech Transmission Index). The methods of measuring STI and RASTI, including the limitations of applying the two parameters, are described in IEC 60268-16:1998.

A.3 Articulation loss of consonants, Alcons, for speech A measure for evaluating speech intelligibility in rooms is the articulation loss of spoken consonants, Alcons, which is essentially a function of the signal/noise separation S/N and the reverberation time, as well as geometrical parameters. Long reverberation times lead to a higher articulation loss, since the reverberation time, like noise, affects the useful signals and thus reduces intelligibility.

A.4 Common Intelligibility Scale, CIS This physical measure, as a general scale for speech intelligibility, cannot be directly measured, but represents a formulaic relationship between STI and Alcons: CIS = 1 + lg (STI)

(A.3)

CIS = 1 + lg {0,9482 – 0,1845 × ln (Alcons)}

(A.4)

The relationship between STI, Alcons and CIS is shown in table A.1.

Column

1

2

3

STI value

Alcons

CIS

1

0 to 0,3

> 34 %

< 0,48

2

0,3 to 0,45

34 % to 15 %

0,48 to 0,65

3

0,45 to 0,6

15 % to 7 %

0,65 to 0,78

4

0,6 to 0,76

7 % to 3 %

0,78 to 0,88

5

0,75 to 1,0

75 dB, starts to distort and is therefore more difficult to understand. For transmission in the room, the room configuration should convey as much initial sound energy as possible to all the listener locations directly (or with the aid of reflections); interference caused by too high a total noise pressure level, reverberation times that are too long, and energy-rich reflections that are too late should be avoided. For the listener, speech comprehension should be possible without interference. Speech intelligibility is primarily characterized by the difference between the speech s.p.l. and the total noise s.p.l. (LSA – LNA), where the former is measured at the listener location and the latter is the effective total noise pressure level. The effect of the diffuse sound field (reverberation) also contributes to LNA. Speech intelligibility that is largely interference-free can be expected at speech/noise separations of 10 dB to 20 dB. Model calculations and experience show that speech intelligibility is greater where the noise level (LNA = 30 dB to 40 dB), and reverberation time (T = 0,3 s to 1 s) are lowest. Since it is not practical to perform calculations for each room, especially where room usage and speaking and hearing abilities vary greatly, this standard specifies general

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DIN 18041:2004-05

acoustic requirements (see clauses 4 and 6). Two essential aspects, hearing ability, and the ability to speak and understand the language that is being communicated, must be considered when ensuring spoken communication. To participate in spoken communication, listeners with reduced hearing ability require a 5 dB to 15 dB higher speech/noise separation and lower reverberation times than do those with good hearing (see Annex C). Spoken communication requires the speaker and listener to speak the same language and understand each other. For communication with specialised texts or in a foreign language, the speech/noise separation is to be 5 dB to 10 dB higher. By increasing the sound power level and the directionality of normal speech — by means of special loudspeaker arrangements — sound systems can increase the direct component of speech, and thus the speech/noise level separation.

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DIN 18041:2004-05

Bibliography

DIN EN ISO 11690-1, Acoustics — Recommended practice for the design of low-noise workplaces containing machinery — Part 1: Noise control strategies DIN EN ISO 11690-2, Acoustics — Recommended practice for the design of low-noise workplaces containing machinery — Part 2: Noise control measures DIN 18032-1, Halls and rooms for sports and multi-purpose use — Part 1: Planning principles ISO 31-7, Quantities and units — Part 7: Acoustics IEC 60268-26:1998, Sound system equipment — Part 16: Objective rating of speech intelligibility by speech transmission index VDI 2058 Part 2:1988-06, Beurteilung von Lärm hinsichtlich Gehörgefährdung (Assessment of noise with regard to risk to hearing) VDI 2058 Part 3:1999-02, Beurteilung von Lärm am Arbeitsplatz unter Berücksichtigung unterschiedlicher Tätigkeiten (Assessment of noise in the workplace with regard to various operations) C. Ruhe. Günstige Raumakustik hilft Hörgeschädigten (Favourable room acoustics help the hearing impaired) Berat. Ing. (Consulting Engineer), 12/1998, p. 45.

[2]

D. J. MacKenzie & S. Airey. Classroom Acoustics — Summary Report 1999; Heriot-Watt University, Edinburgh; Department of Building Engineering and Survey, Riccarton, Edinburgh, EHI4 4AS.

[3]

W. Fasold, W. Kraak & W. Schirmer (editors). Taschenbuch der Akustik. Bd. 1 & 2 (Handbook of acoustics, Volumes 1 and 2) VEB Verlag, Berlin 1984.

[4]

W. Fasold & E. Veres. Schallschutz und Raumakustik in der Praxis. (Noise control and room acoustics in practice) Verlag für Bauwesen, Berlin 1998.

[5]

K. Eggenschwiler et al. Beschallungsanlagen für Sprache — Empfehlungen für Architekten und Bauherrschaften (Sound systems for speech — Recommendations for architects and builders) Ed.: Schweizerische Gesellschaft für Akustik, January 2001.

[6]

Glen M. Ballou (editor). Handbook for Sound Engineers, Third Edition. Focal Press, Boston, Oxford, Auckland, Johannesburg, Melbourne, New Delhi 2002.

[7]

Ch. Thiel. Schallabsorptionsgradtabellen. (Sound absorption coefficient tables) Bauakademie der DDR, Bauinformation, Berlin 1969 to 1978.

[8]

Technische Hilfen für Hörgeschädigte. (Technical aids for the hearing impaired) DSB-Ratgeber (DSB Guides), 11, Deutscher Schwerhörigenbund e.V., Breite Straße 23, 13187 Berlin, October 2002.

[9]

E. Meyer, D. Kunstmann, & H. Kuttruff. Über einige Messungen zur Schallabsorption von Publikum (Regarding some measurements of sound absorption by the public), Acustica, 14 (1964), p. 119–124.

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[1]

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