EN ISO 3382:2000
(Main)Acoustics - Measurements of the reverberation time of rooms with reference to other acoustical parameters (ISO 3382:1997)
Acoustics - Measurements of the reverberation time of rooms with reference to other acoustical parameters (ISO 3382:1997)
This document specifies methods for the measurement of reverberation time in rooms. It is not restricted to auditoria or concert halls; it is also applicable to rooms intended for speech and music or where noise protection is a consideration. It describes the measurement procedure, the apparatus needed, the coverage required, and the method of evaluating the data and presenting the test report. Furthermore, it is intended for application of modern digital measuring techniques and for evaluation of room acoustical parameters derived from impulse responses.
Akustik - Messung der Nachhallzeit von Räumen mit Hinweis auf andere akustische Parameter (ISO 3382:1997)
Diese Internationale Norm legt Verfahren zur Messung der Nachhallzeit in Räumen fest. Sie ist nicht nur auf Zuhörersäle oder Konzertsäle beschränkt, sondern auch anwendbar, wo der Schallschutz Anlaß der Messung ist. Sie beschreibt das Meßverfahren, die notwendigen Meßgeräte, die erforderliche Meßpunktdichte, sowie das Auswerteverfahren und die Abfassung des Prüfberichts. Ferner sollte sie zur Anwendung moderner digitaler Meßtechnik und zur Auswertung raumakustischer Parameter führen, die aus Impulsantworten abgeleitet werden.
Acoustique - Mesurage de la durée de réverbération des salles en référence à d'autres paramètres acoustiques (ISO 3382:1997)
Fournit des méthodes de mesure pour les caractéristiques les plus
importantes des récepteurs de communications à usage général.
Le contenu du corrigendum de février 1997 a été pris en considération dans cet exemplaire.
Akustika - Merjenje odmevnega časa prostorov z upoštevanjem drugih akustičnih parametrov (ISO 3382:1997)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 3382:2001
01-september-2001
$NXVWLND0HUMHQMHRGPHYQHJDþDVDSURVWRURY]XSRãWHYDQMHPGUXJLKDNXVWLþQLK
SDUDPHWURY ,62
Acoustics - Measurements of the reverberation time of rooms with reference to other
acoustical parameters (ISO 3382:1997)
Akustik - Messung der Nachhallzeit von Räumen mit Hinweis auf andere akustische
Parameter (ISO 3382:1997)
Acoustique - Mesurage de la durée de réverbération des salles en référence a d'autres
parametres acoustiques (ISO 3382:1997)
Ta slovenski standard je istoveten z: EN ISO 3382:2000
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
91.120.20 $NXVWLNDYVWDYEDK=YRþQD Acoustics in building. Sound
L]RODFLMD insulation
SIST EN ISO 3382:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 3382:2001
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SIST EN ISO 3382:2001
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SIST EN ISO 3382:2001
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SIST EN ISO 3382:2001
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SIST EN ISO 3382:2001
INTERNATIONAL IS0
STANDARD
3382
Second edition
1997-06- 15
Acoustics - Measurement of the
reverberation time of rooms with reference
to other acoustical parameters
Acoustique - Mesurage de la d&e de rherbkation des sales en
rgfbrence 2 d ’autres paramhtres acoustiques
Reference number
IS0 3382: 1997(E)
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SIST EN ISO 3382:2001
IS0 3382: 1997(E)
Contents
1
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*.~.~~.~~.~.~~.~~~~.~~~~~.~.~~.~*.~~~*.~~.~ “*~~~~.~~~~~.~~~~~~ “. ”~~
1
2 Normative references .,.~.,.~.~.*.~.~.~.~~.~~.*.~~~.~~~~.~*.~~~~~.~.,.~,.
1
3 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.=. “~.~~.~.~~.~**.~~.~.~.~~.~~~.~~~.~~~.~~~.~~~.~.~~~~.~~.~~~.~.~.~.~
2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~.~.~~.~.~.~.~~~.~~.~~*~~.~.~~.~.~~.*.~.~~.
4 Measurement conditions
2
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.~.~.~~~~.~.~.~~.~~~~*~~ “.~.~.~.~.~.~~~.~~ ‘.~.~~~.
3
4.2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~~.~.~.~~~.~.~~~~~.~.~.~.~.~.~.~.~.~.~~.
4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~~.~. “.*.**.*.~.~~.~~~~*~.~.~*~~~~~~~~.~.~.~~~.~ “.~~“”
4.3 Measurement positions
6
5 Measurement procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~. ”.~.~.~.~.
6
5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~.~.~.*~~.~.~.~~~~.~.~~.~.~.~~~.~.~~.~~~.~*~.~~~
6
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~. “.~.
5.2 Interrupted noise method
7
. . . . . . . . . . . . . . . . . . . ‘.*.~.~*~.*~.~~~.~.~.~~.”
5.3 Integrated impulse response method
a
..,......,..,...........................................~..........,...................,...,,.,,..~......,~......,...,..............
6 Evaluation of decay curves
a
. . .*.~.~.~.
6.1 Interrupted noise method
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~. ‘. 9
6.2 Integrated impulse response method
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.*.~.~.~. ”. 9
6.3 Non-linear decay curves
.~.,.~.~.,.,,.,. 9
6.4 Lower limits for reliable results caused by filter and detector
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~.
7 Spatial averaging
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~.~.~.~. ”.~.
a Statement of results
10
8.1 Tables and curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.~. ‘.~.~ ”.~~.~~.~~.~.~.~ ‘.
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .==.*.
8.2 Test report
. . . . . . . . . . . . . . . . . .~~. 12
Annex A (informative) Auditorium measures derived from impulse responses
. . . . . .*m. 19
Annex B (informative) Binaural auditorium measures derived from impulse responses
.,.,.,.,,.~.,.,. 21
Annex C (informative) Bibliography
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
c=ch; a=400net; p=iso; o=isocs; sxentral
x.400
Printed in Switzerland
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SIST EN ISO 3382:2001
0 IS0 IS0 3382: 1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard IS0 3382 was prepared by Technical Committee ISORC 43, Acoustics, Subcommittee SC 2,
Building acoustics.
This second edition cancels and replaces the first edition (IS0 3382:1975), which has been technically revised.
Annexes A, B and C of this International Standard are for information only.
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SIST EN ISO 3382:2001
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IS0 3382:1997( E)
Introduction
The reverberation time of a room used to be regarded as the predominant indicator of its acoustical properties.
Whilst reverberation time continues to be regarded as a significant parameter, there is reasonable agreement that
other types of measurements such as relative sound pressure levels, early/late energy ratios, lateral energy
fractions, interaural cross correlation functions and background noise levels are needed for a more complete
evaluation of acoustical quality of rooms. This International Standard continues to specify room acoustic quality by
reverberation time alone, but introduces two other levels of complexity in room acoustics measurement.
Annex A presents measures based on squared impulse responses: a further measure of reverberation (early decay
time) and measures of relative sound levels, early/late energy fractions and lateral energy fractions in auditoria.
Within these categories there is still work to be done in determining which measures are the most suitable to
standardize on but, since they are all derivable from impulse responses, it is appropriate to introduce the impulse
response as the basis for standard measurements. Annex B introduces binaural measurements and the head and
torso simulators (dummy heads) required to make the measurements in auditoria.
Reverberation time measurements are important in the field of noise control in rooms as well as for the assessment
of rooms for speech and music; this International Standard also applies to measurements in these enclosures.
However, it does not apply to laboratory measurements in test facilities or reverberation rooms. Laboratory
measurements require other specifications of averaging single measurements at prescribed source and microphone
positions. This International Standard establishes a method for obtaining reverberation times from impulse
responses and from interrupted noise. In the annexes, the concepts and details of measurement procedures for
some of the newer measures are introduced, but these annexes do not constitute a part of the formal specifications
of this standard. The intention is to make it possible to compare reverberation time measurements with higher
certainty, and to promote the use of and consensus in measurement of the newer measures.
IV
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SIST EN ISO 3382:2001
IS0 3382:1997( E)
INTERNATIONAL STANDARD o IS0
Acoustics - Measurement of the reverberation time of rooms with
reference to other acoustical parameters
1 Scope
This International Standard specifies methods for the measurement of reverberation time in rooms. It is not
restricted to auditoria or concert halls; it is also applicable to rooms intended for speech and music or where noise
protection is a consideration. It describes the measurement procedure, the apparatus needed, the coverage
required, and the method of evaluating the data and presenting the test report. Furthermore, it is intended for
application of modern digital measuring techniques and for evaluation of room acoustical parameters derived from
impulse responses.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards listed below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
IS0 3741 :I 988, Acoustics - Determination of sound power levels of noise sources - Precision methods for broad-
band sources in reverberation room.
IS0 57252:1994, Accuracy (trueness and precision) of measurement methods and results - Pat? 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method.
IEC 268-1 :I 985, Sound system equipment - Part I: General.
I EC 651: 1979, Sound /eve/ meters.
Octave-band filters and fractional-octave-band filters.
IEC 1260: 1995, Electroacoustics -
ITU Recommendation P.58:1994, Head and torso simulator for telephonometry.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 decay curve:
after the source of
Decay of sound press ure level as a fu nction of time at one point of the room sound has ceased.
of a conti nuous sound source in the room or derived
NOTE 1 This decay may be either measured after the actual cut-off
from the reverse-time integrated squa red impulse response of the room.
NOTE 2 The decay irectly obtained after non-continuous excitation of a room (e.g. by recording a gunshot with a level
recorder) is not recommended for accurate evaluation of the reverberation time. This method should only be used for survey
purposes.
Method of obtaining decay curves by direct recording of the decay of sound pressure level after exciting a room with
broadband or band limited noise.
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3.3 integrated impulse response method:
Method of obtaining decay curves by reverse-time integration of the squared impulse responses.
3.4 impulse response:
Plot as a function of time of the sound pressure received in a room as a result of excitation of the room by a Dirac
delta function.
NOTE 3 It is impossible in practice to create and radiate true Dirac delta functions but short transient sounds (e.g. from
gunshots) may offer close enough approximations for practical measurement. An alternative measurement technique, however,
is to use a period of maximum-length sequence type signal (or other deterministic, flat-spectrum signal) and transform the
measured response back to an impulse response.
3.5 reverberation time, T:
Time, expressed in seconds, that would be required for the sound pressure level to decrease by 60 dB, at a rate of
decay given by the linear least-squares regression of the measured decay curve from a level 5 dB below the initial
level to 35 dB below.
NOTE 4 Where a decay curve is not monotonic the range to be evaluated is defined by the times at which the decay curve
first reaches 5 dB and 35 dB below the initial level respectively. A value for T based on the decay rate over a smaller dynamic
range (down to a minimum of 20 dB extending from 5 dB down to 25 dB down) is also allowable provided the results are
appropriately labelled. In the case of ambiguity the measure for T using the decay between 5 dB and 35 dB should be called
TaoUsing ’ 5 dB and 25 dB, the result should be labelled Tzo and similarly for other evaluation ranges.
3.6 States of occupancy
NOTE 5 Reverberation time measured in a room will be influenced by the numbe r of people present and the following states
of occupancy are defined for measurement purposes.
NOTE 6 An accurate description of the state of occupancy of the room is of decisive importance in assessing the results
obtained by measuring the reverberation time.
NOTE 7 In theatres, a distinction shall be made between “safety curtain up” and “safety curtain down ”, between “orchestra
pit open” and “orchestra pit closed ”, and also between “orchestra seated on the stage” with and without concert enclosure. In
all these cases, measurement may be useful. If the safety curtain is up, the amount of furnishing of the stage is of importance
and shall be described.
3.6.1 unoccupied state:
State of the room prepared for use and ready for speakers or performers and audience, but without these persons
present; for concert halls and opera houses the presence of chairs for performers, music stands and percussion
instruments etc. shall be taken into account.
3.6.2 studio state (only for rooms for speech and music):
State of the room occupied by the performers or speakers only (without audience), for example at rehearsals or
during sound recordings; the number of performers and other persons, such as technicians, corresponding to the
usual number.
3.6.3 occupied state:
State of an auditorium or theatre when 80 % to 100 % of the seats are occupied
NOTE 8 Extraordinary occupancies (such as that which would be created in a concert hall by a larger than usual orchestra or
the additional presence of a choir or standees) should be noted with the results.
4 Measurement conditions
4.1 General
The measurements of reverberation time may be made with the room in any or all states of occupancy. Where the
room has adjustable components for providing variable acoustical conditions, it may be relevant to carry out
separate measurements with these components in each of their normal settings. The temperature and relative
humidity of the air in the room should be measured to an accuracy of * 1 OC and * 5 % respectively.
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ISO3382:1997( E)
Where variable components involve active (i.e. electronic) techniques then the effects of these should be measured,
NOTE 9
too, but as certain types of electronic reverberation enhancement systems create non-time-stationary conditions in the room, a
unique impulse response will not exist and caution should be exercised in using synchronous averaging during the course of
making measurements.
4.2 Equipment
42.1 Sound source
The sound source should be as close to omni-directional as possible. It shall produce a sound pressure level
sufficient to provide decay curves with the required minimum dynamic range without contamination by background
noise (see 3.5). Commercial domestic loudspeakers are not acceptable as an omni-directional source. In the case
of measurements of impulse responses using pseudo-random sequences, the required sound pressure level might
be quite low because a strong improvement of the signal to noise ratio by means of correlated averaging is
possible. In the case of measurements which do not use a synchronous averaging (or other) technique to augment
the decay range then a source level will be required which gives at least 45 dB above the background level in the
corresponding frequency band. If only TgO is to be measured it is sufficient to create a level at least 35 dB above the
background level.
4.22 Microphones, recording and analysis equipment
Omni-directional microphones shall be used to detect the sound pressure and the output may be taken either
directly to an amplifier, filter set and a system for displaying decay curves or analysis equipment for deriving the
-
impulse responses, or
to a signal recorder for later analysis.
4.2.2.1 Microphone and filters
The measurement equipment shall meet the requirements of a type 1 sound level meter according to IEC 651. The
octave or one-third-octave filters shall conform with IEC 1260. The microphone should be as small as possible and
preferably have a maximum diaphragm diameter of 13 mm. Microphones with diameters up to 26 mm are allowed, if
they are of the pressure response type or of the free field response type but supplied with a random incidence
corrector yielding a flat frequency response at random incidence.
4.2.2.2 Tape recorder
If the sound decay is initially recorded on magnetic tape, automatic gain control or other circuits for dynamic
optimisation of signal-to-noise ratio shall not be used. A relatively long tape recording shall be made of each decay
to enable determination of the final background level following the decay.
The tape recorder shall have the following characteristics, for the particular combination of record and playback
speeds used:
a) the frequency response shall be flat over the frequency range of measurement within a tolerance of * 3 dB;
b) the dynamic range shall be sufficient to allow the required minimum decay curve range. In the case of
interrupted noise decays the recorder shall be capable of providing a signal-to-noise ratio of at least 50 dB in
every frequency band concerned;
within * 2 %, where ~1 is an integer including
c) the ratio of the playback speed to the record speed shall be 10°,O1n
zero.
NOTE 10 If speed translation is used on playback, the corresponding frequency translation will then be a whole number of
standard one-third-octave band spacings or if IZ is a multiple of three, of octave band spacings.
NOTE 11 Where a tape recorder is used then in the requirements in 4.2.2.3 below concerning the speed of response of the
apparatus for forming a record of the decay of sound pressure level with time, T refers to the effective reverberation time of the
signal being played back. This will differ from the true reverberation time of the enclosure only if the playback speed differs
from the record speed.
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NOTE 12 When the decay has been recorded for replay through filters and an integrating device, it can be beneficial to
time-reverse the responses during replay (see [4]).
4.2.2.3 Apparatus for forming decay record of level
The apparatus for forming (and displaying and/or evaluating) the decay record shall use any of the following:
exponential averaging, with continuous curve as output;
a)
exponential averaging, with successive discrete sample points from the continuous average as output;
c) linear averaging, with successive discrete linear averages as output (in some cases with small pauses between
performance of averages).
The average time, i.e. time constant of an exponential averaging device (or appropriate equivalent) shall be less
than, but as close as possible to T/20. Similarly, the averaging time of a linear averaging device shall be less
than Tn. (Here T is the reverberation time being measured or, if appropriate, the effective reverberation time as
described in note 11 above.)
In apparatus where the decay record is formed as a succession of discrete points, the time interval between points
on the record shall be less than I,5 times the averaging time of the device.
In all cases where the decay record is to be evaluated visually, adjust the time scale of the display so that the slope
of the record is as close as possible to 45*.
exponential ave raging device is equal to 4,34 divided by the decay rate in Is per
NOTE 1 3 The averaging time of an
second of the device.
sound pressure level is recorded graphically as a function of time, are
NOTE 14 Commercial level recorders, in which
devices
approximately equivalent to exponential averaging
NOTE 15 When an exponential averaging device is used there is little advantage in setting the averaging time very much less
than T/20. When a linear averaging device is used there is no advantage in setting the interval between points at very much
less than T/7. In some sequential measuring procedures it is feasible to reset the averaging time appropriately for each
frequency band. In other procedures this is not feasible, and an averaging time or interval chosen as above with reference to
the shortest reverberation time in any band has to serve for measurements in all bands.
4.2.2.4 Overload indication
No overloading shall be allowed in any stage of the measuring apparatus. Where impulsive sound sources are
used, peak-level indicating devices shall be used for checking against overloading.
4.3 Measurement positions
As measurements may be required for different purposes the number of measurement positions are chosen in order
to achieve an appropriate coverage in the room. Microphone positions shall be at least half a wavelength apart, i.e.
a minimum distance of around 2 m for the usual frequency range. The distance from any microphone position to the
nearest reflecting surface, including the floor, shall be at least a quarter of a wavelength, i.e. normally around 1 m.
No microphone position shall be too close to any source position in order to avoid too strong influence from the
in metres, can be calculated from:
direct sound. The minimum distance d,i ”,
-2 v
d
min -
CT
i
where
V is the volume, in cubic metres;
c is the speed of sound, in metres per second;
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T is an estimate of the expected reverberation time’ in seconds.
NOTE 16 In small rooms with very short reverberation time (e.g. talks studios) it may be impossible to fulfil the above
requirement. In such cases, and only for the measurement of reverberation time, it is recommended that the direct sound is
eliminated by insertion of a barrier (with negligible sound absorption) between source and receiver.
of one source position The number of
Each pair of measurement positions is a combination and one microphone position.
positions can be chosen to yield either a low coverage or a normal coverage.
4.3.1 Low coverage (least measurement effort)
Measurements are made for assessment of the amount of room absorption for noise control purposes, including
measurement of sound reduction index, or assessment of the reverberation time for sound system calculations.
Make measurements of T for two source positions which are representative of those where noise sources are
located or of those used by performers and find the average of results from three or four microphone positions in
areas where people normally are present or in “centre of seating” areas. If the deviations between the results from
the single positions extend the tolerances set for the purpose of the measurement, use more positions.
4.3.2 Normal coverage
Measurements made for verification of building performance against a design brief.
Choose the number and location of source positions so as to include all areas likely to be occupied by performers
(e.g. upon stage, risers, orchestra pits and choral seating) in addition to main stage areas. A minimum of two source
positions shall be used.
A distribution of microphone positions shall be chosen which anticipates the major influences likely to cause
differences in reverberation time throughout the room. Obvious examples are the differences for seating areas close
to walls, underneath balconies or in spaces which are decoupled (e.g. in church transepts and chancels compared
with church naves). This requires a judgement of the evenness of the “acoustical” distribution to the different seating
areas, the equality of the coupling of the separate parts of the volume and the proximity to local perturbations. For
reverberation time measurement, it may be useful to assess the room against the following criteria (which in many
cases will simply require a visual assessment) to determine whether single spatial averages will adequately
describe the room:
a) the materials of the boundary surfaces and any suspended elements are such that, judged in terms of their
absorption and diffusion properties, they are reasonably evenly distributed amongst the surfaces which
surround the room, and
b) all parts of the room volume communicate reasonably equally with each other, then three or four microphone
positions will be adequate - these positions being chosen to cover the seating area, in an evenly spaced
and the results of the measurements may be averaged. In rooms for speech and music the height of
array -
the microphones above the floor should be I,2 m corresponding to the ear height of average listeners in typical
chairs.
NOTE 17 For a) above, if the ceiling, side, front and rear walls, when assessed individually, have no regions, covering more
than 50 % of their respective areas, with properties different from those of the remaining surfaces, then it may be considered
that the distribution is acceptably even. (In some spaces it may be helpful to approximate the room geometry to a rectangular
parallelepiped for this assessment.)
may be considered to operate as a single space if there are no
NOTE 18 For b) above, the room volume parts of the floor
blocked to any other part of the room which is more than 10 % of the total
area which have their lines-of-sight room volume
NOTE 19 If conditions of notes 17 and 18 are not satisfied then the room is likely to show areas with differing reverberation
times, and these should be investigated and measured separately.
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5 Measurement procedures
5.1 General
Two methods of measuring the reverberation time are described in this standard: the interrupted noise method and
the integrated impulse response method. Both methods have the same expectation value but the latter requires
more sophisticated instrumentation. If room acoustic measures other than the reverberation time are to be
measured only the latter method is relevant, as these are based on the impulse response.
It is preferable to measure reverberation times in octave bands from 63 Hz to 4 kHz in concert halls and rooms for
NOTE 20
speech. For measurements in rooms for other purposes measurements in one-third-octave bands from 100 Hz to 5 kHz can be
applied.
5.2 Interrupted noise method
Excitation of the room
52.1
A loudspeaker source shall be used and the signal fed into the loudspeaker shall be derived from broadband
random or pseudo-rando
...
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