🏗️ Sound absorption in a reverberation room — sound absorption coefficient αs of wall and ceiling materials and equivalent sound absorption area of objects (furniture, screens, persons, space absorbers) from the reverberation time of the empty room and of the room with the specimen, by the interrupted noise method or the integrated impulse response method, one-third-octave bands 100–5000 Hz; PN-EN ISO 354

Construction PN-EN ISO 354

Overview

WHAT THE STANDARD COVERS. ISO 354:2003 (clause 1) specifies a method of measuring, in a reverberation room, the sound absorption coefficient of acoustical materials used as wall or ceiling treatments, or the equivalent sound absorption area of objects such as furniture, persons or space absorbers. It is not intended for measuring the absorption characteristics of weakly damped resonators. The results can be used for comparison purposes and for design calculations in room acoustics and noise control. According to the introduction, the sound field in a properly designed reverberation room closely approximates a diffuse field, in which sound reaches the surfaces at random incidence — so absorption measured in the room closely approximates absorption under the conditions assumed as the basis of standardization.

ACCORDING TO THE TEXT OF ISO 354:2003 — EDITION AND TERMS (foreword, clauses 2–4). The standard was prepared by technical committee ISO/TC 43 Acoustics, subcommittee SC 2 Building acoustics. The second edition replaced ISO 354:1985; changes: the integrated impulse response method was introduced, the requirement to measure at least 36 decays was added, mounting conditions from ISO 354:1985/Amd.1:1997 and mountings Type B and Type J were introduced. The European EN ISO 354:2003 was approved by CEN on 23 April 2003 (prepared with committee CEN/TC 126) and adopted the ISO text without modifications; it superseded EN ISO 354:1993. Normative references: ISO 266 (preferred frequencies), ISO 9613-1 (absorption of sound by the atmosphere), IEC 61260 (octave-band and fractional-octave-band filters). Terms: reverberation time T — the time that would be required for the sound pressure level to decrease by 60 dB after the source has stopped (it can be obtained by linear extrapolation of shorter ranges); interrupted noise method — decay curves recorded directly after exciting the room with broadband or band-limited noise; integrated impulse response method — decay curves obtained by reverse-time integration of the squared impulse response (note of the standard: the impulse response can be obtained from short transient sounds, e.g. shots, or from an MLS signal or another deterministic flat-spectrum signal). Equivalent sound absorption area of the room — A1 of the empty room, A2 of the room with the specimen; AT — their difference; S — the area of floor or wall covered by the specimen (with a Type E or J mounting — the area enclosed by the structure). Sound absorption coefficient αs = AT/S; for absorbers exposed on both sides it is divided by the area of both sides. Notes of the standard: αs from reverberation time measurements can be larger than 1.0 (e.g. because of diffraction), so it is not expressed as a percentage; the subscript “s” distinguishes it from the “geometric” plane-wave absorption coefficient, which is always smaller than 1.0. Principle (clause 4): the average reverberation time is measured with and without the specimen, AT is calculated with Sabine’s equation (8.1.2.1 — only a cross-reference in the fragment read), for several identical objects Aobj = AT/n.

MEASUREMENT CONDITIONS (clauses 5–7.1). One-third-octave bands with centre frequencies 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000 and 5000 Hz according to ISO 266; additional bands outside this range are allowed, but below 100 Hz accurate results are difficult because of the low modal density of the room. Room: volume at least 150 m³ (for new rooms at least 200 m³ strongly recommended; above about 500 m³ measurement at high frequencies may be inaccurate because of air absorption); a shape meeting the condition lmax < 1.9 V^(1/3), where lmax is the longest straight line fitting within the room (in a rectangular room — the major diagonal); no two dimensions in the ratio of small whole numbers; stationary or suspended diffusers or rotating vanes (Annex A — title). The equivalent sound absorption area of the empty room A1 must not exceed the values of Table 1 (for V = 200 m³: 6.5 m² in the bands 100–800 Hz, 7.0 m² at 1000 Hz, 7.5 at 1250, 8.0 at 1600, 9.5 at 2000, 10.5 at 2500, 12.0 at 3150, 13.0 at 4000 and 14.0 m² at 5000 Hz; for another volume they are multiplied by (V/200 m³)^(2/3)); the graph of A1 against frequency must be smooth, without values differing by more than 15 % from the mean of both adjacent bands. Plane specimen: 10–12 m² (for V > 200 m³ the upper limit is multiplied by (V/200 m³)^(2/3); for low absorption the upper limit is chosen), a rectangle with a width-to-length ratio of 0.7–1, not closer than 1 m to any room edge (should), at least 0.75 m (shall), edges preferably not parallel to the nearest room edge; heavy specimens may stand vertically against a wall on the floor — then the 0.75 m requirement does not apply. Mounting according to Annex B unless the producer’s specification or the application requires another; the empty room is measured without the frame and side walls of the specimen (except the barrier around a Type J mounting). Objects: pads and baffles — Type J mounting; chairs, free-standing screens, persons — as installed in practice, not closer than 1 m to other boundaries; space absorbers at least 1 m from any boundary, diffusers and microphone; generally at least three objects, so that the change in the equivalent sound absorption area of the room is between 1 m² and 12 m² (for V > 200 m³ — multiplied by (V/200 m³)^(2/3)), arranged randomly at least 2 m apart; a single object is tested in at least three locations at least 2 m apart and averaged. Climate: relative humidity 30–90 %, temperature at least 15 °C throughout the test, conditions in the empty room and with the specimen almost the same, corrections for the change in air absorption (8.1.2.3 — title) always applied; the specimen must reach equilibrium with the room. Methods (7.1): the decay curve from the interrupted noise method is the result of a statistical process — averaging several decay curves or reverberation times at one microphone and loudspeaker position is mandatory; the integrated impulse response is a deterministic function and needs no averaging, but requires more sophisticated instrumentation and data processing. Microphones omnidirectional, positions at least 1.5 m apart, 2 m from any source and 1 m from any surface and from the specimen; decay curves from different microphone positions must not be combined. Source omnidirectional, source positions at least 3 m apart.

WHAT ELSE IS IN THE STANDARD (table of contents — only titles in the fragment read). 7.2 Interrupted noise method, 7.3 Integrated impulse response method, 7.4 Evaluation of reverberation times based on decay curves; 8.1 Method of calculation, 8.2 Precision, 8.3 Presentation of results; 9 Test report; Annex A (normative) — diffusivity of the sound field in the reverberation room; Annex B (normative) — test specimen mountings for sound absorption tests.

STATUS (PKN card as of 07.11.2026). Card PN-EN ISO 354:2005 (Polish version) without a withdrawal label: published 29-06-2005, 29 pages, Building and Building Structures Sector, KT 253 Architectural Acoustics, “Implements: EN ISO 354:2003 [IDT], ISO 354:2003 [IDT]”, “Replaces: PN-EN 20354:2000 - Polish version, PN-EN 20354:2000/A1:2000 - Polish version”, ICS 17.140.01, 91.120.20. Searching “PN-EN ISO 354” in the PKN catalogue returns only this card — there is no other edition or foreign-language version in the catalogue. ISO page (read 07.11.2026): ISO 354:2003, edition 2, published 2003-05, 21 pages, ISO/TC 43/SC 2, stage 90.93 “International Standard confirmed” — last reviewed and confirmed in 2024; the page shows no entry about a new edition.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, read 07.11.2026; “Laboratories” tab on labcoda.pl, 07.11.2026). The notation “ISO 354” appears in 8 records at 5 Polish laboratories: AB 023 (2), AB 054 (1), AB 1241 (2), AB 1271 (2), AB 818 (1). Five of them are test items, three — “EN ISO 354” at AB 023, AB 1241 and AB 1271 — are rows of the table of assessment of performance of construction products under Regulation (EU) No 305/2011, at the essential characteristic “sound absorption”. Notations in the test items: “PN-EN ISO 354:2005 „N”” (AB 1271, AB 818), “PN-EN ISO 354 „N”” without year (AB 1241), “PN-EN ISO 354 „N” z wyłączeniem pkt. 7.3.1” (excluding point 7.3.1; AB 023) and “PN-EN ISO 354:2005 z wyłączeniem pkt. 7.3.1.” (AB 054); “N” is, according to the scope legend, a test method used in activities relevant to notification under Regulation (EU) No 305/2011. AB 1271 cites in the same item ISO 20189:2018 (screens, furniture and single objects for interior use — rating of sound absorption; ISO page, read 07.11.2026: edition 1 of 2018-11, confirmed in 2024). Outside Poland the notation “ČSN EN ISO 354” appears in 6 records at 5 Czech laboratories (1007.1, 1007.4 — 2, 1018.3, 1145, 1787). NOT included in the set is the notation “PN-EN 354:2012” and “EN 354:2010” at AB 1975 (2 records) — this is a different standard: according to the PKN card, PN-EN 354:2012 “Personal protective equipment against falls from a height — Lanyards”, and the AB 1975 items concern the static and dynamic strength of lanyards; for the same reason we do not count 9 records “ČSN EN 354” at 4 Czech laboratories. The “Laboratories” tab (“PN-EN ISO 354”, matching by the beginning of the notation) shows 10 laboratories — these 5 Polish and 5 Czech, with the same number of items as the copy (14), without AB 1975 (tab query on labcoda.pl, 07.11.2026). We have not compared the current PCA scope documents of these laboratories with the copy.

WHAT THE LABORATORIES TEST (database copy, complete items). In all five test items — the sound absorption coefficient in a reverberation room: AB 1241 — construction products: sound-absorbing materials, objects and devices that are interior fittings, road traffic noise reducing devices, acoustic barriers, in one-third-octave bands (50–5000) Hz, by the interrupted noise method; AB 1271 — sound-absorbing materials and systems, interior fittings: screens, furniture and single objects for internal use, sound absorption coefficient and sound absorption area, (100–5000) Hz; AB 818 — sound-absorbing materials and systems, objects and devices that are interior fittings, (100–5000) Hz; AB 054 — building and sound-absorbing materials, interior fittings, sound-absorbing systems, road traffic noise reducing devices and acoustic barriers, (100–5000) Hz; AB 023 — sound-absorbing materials, objects and devices of interior fittings, sound-absorbing systems, (100–5000) Hz, “laboratory method”. Items of the Czech laboratories: the sound absorption coefficient of sound-absorbing materials, objects, structures and products and of acoustic barriers; one item (1007.4) — determination of reverberation time in enclosed rooms.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Preparation: the result depends on the specimen mounting (Annex B — only the title and the names of Types B, E, J in the fragment read); the empty room is measured without the frame and side walls of the specimen — measuring the empty room with the frame changes A1 and therefore AT; a plane specimen smaller than 10 m² or closer than 0.75 m to a room edge (except heavy specimens standing vertically against a wall) does not meet the conditions of the standard. Measurement: the standard range is the bands 100–5000 Hz — values in bands below 100 Hz (scope of AB 1241: 50–5000 Hz) are additional measurements, for which the standard warns that accurate results are difficult; in the interrupted noise method averaging at each position is mandatory, and curves from different microphone positions must not be combined; with different temperature and humidity in the two measurements, the difference in reverberation times contains the change in air absorption, which has to be corrected (8.1.2.3 — title). Two laboratories (AB 023, AB 054) hold the standard in their scope excluding point 7.3.1 — it lies in the clause on the integrated impulse response method (we have not read the content of point 7.3.1); a result obtained with the excluded part is not a result within the accreditation scope. Calculation: αs is a calculated quantity — AT = A2 − A1, and A1 and A2 are determined from reverberation times measured by this method using Sabine’s equation (8.1.2.1 — title), S is the specimen area (with Type E and J mountings — the area enclosed by the structure), and for absorbers exposed on both sides — the area of both sides; truncating values to 1.0 or writing them as percentages changes the result (note 2 to 3.9). For objects the result is not αs but the equivalent sound absorption area Aobj = AT/n in m².

WHAT WE DO NOT GIVE. The fragment of ISO 354:2003 we read (iTeh sample) covers the foreword, introduction, table of contents and clauses 1–7.1.3; from the SIST EN ISO 354:2004 sample we also read the EN title page, the European foreword and the beginning of Annex ZA. We do not give the procedure of methods 7.2 and 7.3 (including the content of the excluded point 7.3.1), the rules for evaluating reverberation time from decay curves (7.4), the equations and corrections of clause 8, the precision data (8.2), the presentation of results (8.3), the test report requirements (clause 9) or the content of Annexes A and B — we have not read these parts. We have not read ISO 20189 and do not give its requirements. We have not checked citations of the standard in legislation.

Method principle

In a reverberation room the average reverberation time is measured in one-third-octave bands 100–5000 Hz without and with the specimen — by the interrupted noise method (averaging of decays mandatory) or by the integrated impulse response method; from the reverberation times the equivalent sound absorption areas A1 and A2 are determined, their difference AT is the equivalent sound absorption area of the specimen, and the sound absorption coefficient αs = AT/S or the area of one object Aobj = AT/n (ISO 354:2003, clauses 4–7.1; Sabine’s equation and the corrections of clause 8 — only titles in the fragment read).

Applications

• Acoustical materials used as wall and ceiling treatments — sound absorption coefficient αs (ISO 354:2003, clause 1)
• Objects: furniture, screens, persons, space absorbers, pads and baffles — equivalent sound absorption area of one object
• Data for comparisons and for calculations in room acoustics and noise control; not for weakly damped resonators
• In accreditation scopes: 5 Polish laboratories — sound-absorbing materials and systems, interior fittings, road traffic noise reducing devices and acoustic barriers

Key parameters

Standard

Standard number

PN-EN ISO 354:2005 (Polish version; implements EN ISO 354:2003 and ISO 354:2003 [IDT])

Title (PL)

Akustyka — Pomiar pochłaniania dźwięku w komorze pogłosowej

Title (EN)

Acoustics — Measurement of sound absorption in a reverberation room

Step-by-step procedure

1. Specimen preparation

   Plane specimen 10–12 m² in a mounting from Annex B, or objects arranged as in practice, at least 2 m apart and 1 m from boundaries; establishing the climatic conditions in the room (6.2–6.3).

2. Empty room

   Measurement of reverberation time in the bands 100–5000 Hz without the specimen and without its frame (except the barrier of a Type J mounting), at several microphone and source positions (6.2.1.3, 7.1).

3. Room with specimen

   The same measurement with the specimen mounted, under almost the same conditions of temperature and humidity (6.3.2, 7.1).

4. Calculation

   A1 and A2 from Sabine’s equation with the air absorption correction, AT = A2 − A1, αs = AT/S or Aobj = AT/n (clause 4; 8.1 — title).

5. Result

   αs or Aobj in each one-third-octave band, with a description of the mounting and conditions. PN-EN ISO 354:2005 — current (PKN card as of 07.11.2026; Polish version).

Required equipment and apparatus

Health and safety (OHS)

• Work in the room with loud measurement noise or impulses (e.g. shots) — hearing protection for persons in the room
• Heavy specimens and suspended space absorbers — secure fixing, work at height when suspending
• TECHNICAL NOTE: αs from a reverberation room may exceed 1.0 — it is not truncated to 1.0 and not given as a percentage (note 2 to 3.9)

Frequently asked questions