🏗️ Reverberation time T (T20 from the range 5–25 dB, T30 from the range 5–35 dB below the initial level, extrapolated to 60 dB) in octave or one-third-octave bands in ordinary rooms — interrupted noise method or integrated impulse response method, survey accuracy (2 source–microphone combinations), engineering (6) or precision (12), PN-EN ISO 3382-2

Construction PN-EN ISO 3382-2

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 3382-2:2010, in full (our translation of the Polish card text): “The results of measurements made according to this part of the standard can be used to correct the results of other acoustic measurements, such as the sound pressure level from sound sources or sound insulation measurements. The results can also be used for comparison with requirements for the reverberation time in rooms. They are not intended for use in concert halls and other interiors with special requirements”. We read the text of the standard in the preview of ISO 3382-2:2008 from the cover to clause 5.2.1 (excitation of the room in the interrupted noise method, page 5); we do not have the rest of clause 5.2, clause 5.3 (integrated impulse response method), Clauses 6–9 (evaluation of decay curves, uncertainty, spatial averaging, statement of results) or Annexes A–C.

ACCORDING TO THE TEXT OF ISO 3382-2:2008 (foreword, introduction, Clauses 1–5.2.1). The standard was prepared by ISO/TC 43/SC 2 (building acoustics); Parts 1, 2 and 3 of ISO 3382 together replaced ISO 3382:1997 (Part 1 — performance spaces, Part 3 — open-plan offices). Introduction: three levels of accuracy — survey, engineering and precision — differ mainly in the number of measurement positions; reverberation time is measured because the sound level from noise sources, speech intelligibility and privacy of conversation depend on it, and in order to determine the correction for room absorption in other measurements (sound insulation according to ISO 140, sound power according to ISO 3740); two evaluation ranges are defined, 20 dB and 30 dB, with preference for 20 dB — subjective evaluation of reverberation relates to the early part of the decay, and in field measurements it is often difficult to obtain more than 20 dB (this requires a signal-to-noise ratio of at least 35 dB); Annex B introduces measures of non-linearity and curvature of the decay curve as a warning against abnormal curves; a rotating microphone is accepted only for the interrupted noise method and only when the result is used as a correction; performance spaces are covered by ISO 3382-1, reverberation rooms — by ISO 354. Scope (Clause 1): methods for measuring reverberation time in ordinary rooms — procedure, apparatus, required number of measurement positions, evaluation of data and test report. Normative references: ISO 3382-1, ISO 18233 (new measurement methods), IEC 61260 (octave and one-third-octave filters). Definitions (Clause 3): decay curve; interrupted noise method — direct recording of the level decay after excitation with noise; integrated impulse response method — reverse-time integration of the squared impulse response; the impulse response can be obtained e.g. from an MLS signal or a sine sweep; reverberation time T — the time for the spatially averaged energy density to decrease by 60 dB, in seconds; T20 is determined from the section 5–25 dB below the initial level, T30 — from the section 5–35 dB; large room — above 300 m³. Conditions (4.1): measurement in a room without people, up to two persons may represent the unoccupied state; in precision measurements the air temperature and humidity are measured; air absorption can be neglected if the reverberation time is shorter than 1,5 s at 2 kHz and 0,8 s at 4 kHz. Equipment (4.2): source as omnidirectional as possible (in precision measurements — according to ISO 3382-1, A.3.1); omnidirectional microphones, preferably with a diaphragm diameter up to 14 mm, permitted up to 27 mm (pressure type or free-field type with random-incidence corrector); filters according to IEC 61260; exponential averaging time less than T/30 but as close as possible to it, linear averaging — less than T/12; interval between record points less than 1,5 times the averaging time; no overload at any stage of the chain (with impulsive sources — peak-level indicator). Measurement positions (4.3, Table 1): source–microphone combinations — 2 / 6 / 12, source positions — ≥ 1 / ≥ 2 / ≥ 2, microphone positions — ≥ 2 / ≥ 2 / ≥ 3, number of decays at each position (interrupted noise) — 1 / 2 / 3 (survey, engineering, precision respectively); when the result is used as a correction for other engineering measurements — one source position and three microphone positions suffice; in small rooms one source in a corner; microphones at least about 2 m apart and about 1 m from reflecting surfaces, no symmetrical positions; moving microphone — radius ≥ 0,7 m, plane of traverse not within 10° of the room planes, period ≥ 15 s; minimum microphone–source distance — formula (1): d_min = 2·√(V/(c·T̂)), where V — volume, c — speed of sound, T̂ — estimated reverberation time. Survey method (4.3.2): assessment of absorption for noise control purposes and survey measurements of sound insulation (ISO 10052), octave bands only, nominal accuracy better than 10 %. Engineering method (4.3.3): verification of building performance against requirements for reverberation time or absorption, measurements according to ISO 140; better than 5 % in octaves and 10 % in one-third octaves. Precision method (4.3.4): better than 2,5 % in octaves and 5 % in one-third octaves. Frequency range (5.1): both methods have the same expectation value; without specific requirements — at least 250–2000 Hz for the survey method, 125–4000 Hz in octaves or 100–5000 Hz in one-third octaves for engineering and precision. Excitation (5.2.1): loudspeaker fed with broadband random or pseudo-random noise (stopped randomly); level at least 35 dB above background in the band concerned, and for T30 — at least 45 dB — this is where the part we read ends.

STATUS (cards as of 02.10.2026). The card of PN-EN ISO 3382-2:2010 in the Polish version (published 14-05-2010, 22 pages, price group L) does not carry the heading “Wycofana” (withdrawn): Building and Construction Sector, KT 253 Architectural Acoustics, ICS 91.120.20, “Introduces: EN ISO 3382-2:2008 [IDT], EN ISO 3382-2:2008/AC:2009 [IDT], ISO 3382-2:2008/Cor 1:2009 [IDT], ISO 3382-2:2008 [IDT]”, “Replaces: PN-EN ISO 3382-2:2008 – English version”. PN-EN ISO 3382-2:2008 (English version, published 11-07-2008, replaced PN-EN ISO 3382:2001) — withdrawn 14-05-2010.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 02.10.2026). The number 3382-2 appears in 8 records at 8 laboratories: AB 796, AB 818, AB 838, AB 863, AB 1115, AB 1162, AB 1621, AB 1924. In the current scopes on the PCA website (read on 02.10.2026, issues from 07.02.2025 to 21.07.2026) all 8 cite “PN-EN ISO 3382-2:2010”; AB 818 — “excluding clause 5.3”, i.e. without the integrated impulse response method. No row is set in bold italics. The “Laboratories” tab searches for entries STARTING WITH “PN-EN ISO 3382-2” and shows all 8 laboratories and 8 items — checked with the tab query on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (items in the PCA scopes). Rooms in residential, collective accommodation and public buildings — “reverberation time in octave and 1/3-octave bands, engineering method” (AB 838, AB 863, AB 1115, AB 1924); “reverberation time T20 in 1/1 or 1/3-octave bands”, 50–10 000 Hz, interrupted noise method (AB 796); “reverberation time T20 and T30”, 50–10 000 Hz, interrupted noise method (AB 1621); “reverberation time T10, T20, T30, early decay time EDT”, 50–10 000 Hz, integrated impulse response method and interrupted noise method (AB 1162); “reverberation time”, 100–5000 Hz (with the option of 50, 63 and 80 Hz), rooms except concert halls and rooms with a sound reinforcement system (AB 818). Alongside sound insulation and noise in buildings, at AB 796 also the speech transmission index (PN-EN 60268-16).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Number of positions: the “engineering method” requires at least 2 source positions and 6 independent source–microphone combinations; microphones placed too close together are not independent, and too close to the source (below d_min) they measure direct sound. Dynamic range: T20 requires a decay at least 35 dB above background, T30 — 45 dB; too small a margin above background shortens or lengthens the result. Apparatus: an averaging time longer than T/30 (exponential) or T/12 (linear) overestimates the reverberation time in bands with short reverberation; overload with impulsive sources spoils the curve. Room: people in the room (more than two persons) shorten the reverberation; for a sound insulation correction the number of persons must be the same as in the level measurement. Curve: a non-linear decay (e.g. in coupled rooms) gives different T20 and T30 — the result should be marked as less reliable (Annex B). Designation: the result must be labelled T20 or T30 and the level of accuracy stated.

WHAT WE DO NOT GIVE. We do not have the rest of clause 5.2 (recording and averaging of decays), clause 5.3 (integrated impulse response method), Clause 6 (evaluation of decay curves), Clause 7 (uncertainty), Clause 8 (spatial averaging), Clause 9 (tables, curves, test report) or Annexes A–C — so we do not give the method of fitting the line, uncertainty formulae or the form of the test report.

Method principle

The room is excited with noise from a loudspeaker which is suddenly switched off (interrupted noise method), or the impulse response is recorded and its square integrated backwards in time; from the slope of the decay curve over the section 5–25 dB (T20) or 5–35 dB (T30) below the initial level the time for a 60 dB decrease is determined in octave or one-third-octave bands, averaging the results from the specified number of source–microphone combinations.

Applications

• Rooms in residential, collective accommodation and public buildings — comparison with requirements for reverberation time, 8 laboratories
• Correction for room absorption in sound insulation and sound power measurements
• Classrooms, offices, restaurants, sports halls, railway stations — assessment of room acoustics (not concert halls)

Key parameters

Standard

Standard number

PN-EN ISO 3382-2:2010 (wersja polska; EN ISO 3382-2:2008 IDT z AC:2009, ISO 3382-2:2008 IDT z Cor 1:2009)

Title (PL)

Akustyka — Pomiar parametrów akustycznych pomieszczeń — Część 2: Czas pogłosu w zwyczajnych pomieszczeniach

Title (EN)

Acoustics — Measurement of room acoustic parameters — Part 2: Reverberation time in ordinary rooms

Step-by-step procedure

1. Choice of the level of accuracy

   Survey, engineering or precision according to the purpose of the measurement; frequency range and number of source–microphone combinations according to Table 1 and 5.1. PN-EN ISO 3382-2:2010 current (cards as of 02.10.2026).

2. Preparation of the room

   Room without people (up to two persons permitted); in precision measurements measurement of temperature and humidity.

3. Placing sources and microphones

   Source positions according to use of the room (in small rooms one in a corner); microphones about 2 m apart and about 1 m from surfaces, no symmetry, not closer to the source than d_min = 2·√(V/(c·T̂)).

4. Excitation and decay recording

   Broadband noise at least 35 dB above background (for T30 — 45 dB), switching off and recording the decay in bands (1, 2 or 3 decays per position) — or impulse response measurement (5.3, details NOT GIVEN).

5. Result

   T20 or T30 in bands, averaged over source–microphone combinations; evaluation of curves, uncertainty and report — Clauses 6–9 (NOT GIVEN).

Required equipment and apparatus

Health and safety (OHS)

• High noise level (excitation at least 35–45 dB above background) — hearing protection for operators, no bystanders in the room; the part of the standard we read contains no safety warnings
• SUBSTANTIVE NOTE: T20 and T30 are different quantities for a non-linear decay — the result must state the evaluation range and level of accuracy; the standard does not apply to concert halls (ISO 3382-1)

Frequently asked questions