ISO 17497-1:2004

Acoustics - Sound-scattering properties of surfaces - Part 1: Measurement of the random-incidence scattering coefficient in a reverberation room

ISO 17497-1:2004 specifies a method of measuring the random-incidence scattering coefficient of surfaces as caused by surface roughness. The measurements are made in a reverberation room, either in full scale or on a physical scale model. The measurement results can be used to describe how much the sound reflection from a surface deviates from a specular reflection. The results obtained can be used for comparison purposes and for design calculations with respect to room acoustics and noise control. The method is not intended for characterizing the spatial uniformity of the scattering from a surface.

Acoustique — Propriétés de dispersion du son par les surfaces — Partie 1: Mesurage du coefficient de dispersion sous incidence aléatoire en salle réverbérante

General Information

• Status: Published
• Publication Date: 26-Apr-2004
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• Technical Committee: ISO/TC 43/SC 2 - Building acoustics
• Drafting Committee: ISO/TC 43/SC 2 - Building acoustics
• Current Stage: 9093 - International Standard confirmed
• Start Date: 24-Oct-2024
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 22868:2011 - Forestry and gardening machinery - Noise test code for portable hand-held machines with internal combustion engine - Engineering method (Grade 2 accuracy)
• Effective Date: 06-Jun-2022
• Amended By: ISO 17497-1:2004/Amd 1:2014 - Acoustics - Sound-scattering properties of surfaces - Part 1: Measurement of the random-incidence scattering coefficient in a reverberation room - Amendment 1
• Effective Date: 17-Jul-2021

Overview

ISO 17497-1:2004 - "Acoustics - Sound‑scattering properties of surfaces - Part 1" specifies a laboratory method to measure the random‑incidence scattering coefficient of surfaces caused by surface roughness. Measurements are performed in a reverberation room (full scale or on a physical scale model). Results quantify how much a surface’s reflection deviates from ideal specular reflection and are intended for material comparison and room‑acoustic or noise‑control design calculations. The method does not characterize the directional uniformity (spatial distribution) of scattering.

Key topics and technical requirements

• Measured quantity: random‑incidence scattering coefficient (one minus the ratio of specularly reflected acoustic energy to total reflected energy in a diffuse field).
• Measurement principle: obtain impulse responses for multiple sample orientations on a turntable; use synchronized (phase‑locked) averaging so specular components add coherently while scattered components average out.
• Frequency range: measurements in one‑third‑octave bands covering 100 Hz to 5 000 Hz (full scale); scale models use frequencies scaled by the physical scale ratio.
• Test environment: reverberation room arranged per ISO 354; diffusing elements fixed; temperature and humidity controlled.
• Sample geometry: circular test sample preferred, minimum diameter = N × 3.0 m for physical scale ratio 1:N (square samples allowed with specified edge dimensions and flush mounting).
• Structural depth: method intended for surface roughness; structural depth should be small relative to sample diameter (h ≤ d/16).
• Turntable and base plate: circular rigid base required; base‑plate scattering must be checked and limited to specified values.
• Data processing: measurement of impulse responses, evaluation of decay curves and calculation of scattering coefficient; presentation and reporting per the standard’s clauses.

Applications and who uses it

ISO 17497-1 is used by:

• Acoustic consultants and room‑acoustics designers (concert halls, studios, auditoria)
• Manufacturers of diffusers, acoustic panels, and surface treatments
• Acoustic test laboratories and standards bodies
• Researchers modeling reverberant spaces and noise‑control engineers

Practical uses include material comparison, input data for acoustic simulation/prediction, design of scattering to improve sound diffusion or control reflections, and verification of manufacturing quality.

Related standards

• ISO 354 - Measurement of sound absorption in a reverberation room (test environment requirements)
• ISO 9613‑1 - Outdoor sound attenuation (reference for atmospheric absorption)
• ISO 17497 (Part 2 under preparation) - directional diffusion coefficient (complements Part 1)

Keywords: ISO 17497-1, sound scattering, scattering coefficient, reverberation room, room acoustics, surface roughness, random‑incidence measurement.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17497-1
First edition
2004-05-01
Acoustics — Sound-scattering properties
of surfaces —
Part 1:
Measurement of the random-incidence
scattering coefficient in a reverberation
room
Acoustique — Propriétés de dispersion du son par les surfaces —
Partie 1: Mesurage du coefficient de dispersion sous incidence
aléatoire en salle réverbérante

Reference number
©
ISO 2004
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ii © ISO 2004 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle . 2
5 Frequency range . 3
6 Test arrangement. 4
6.1 Reverberation room. 4
6.2 Turntable and base plate. 4
6.3 Test sample . 5
7 Test procedure . 6
7.1 Test signals . 6
7.2 Source and receiving equipment . 7
7.3 Measurement of impulse responses. 7
7.4 Temperature and relative humidity . 7
7.5 Evaluation of decay curves. 7
8 Expression of results. 8
8.1 Method of calculation . 8
8.2 Precision . 9
8.3 Presentation of results . 10
9 Test report . 10
Annex A (informative) Accuracy of the measurement results. 11
Bibliography . 12

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17497-1 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 2, Building
acoustics.
ISO 17497 consists of the following parts, under the general title Acoustics — Sound-scattering properties of
surfaces:
 Part 1: Measurement of the random-incidence scattering coefficient in a reverberation room
The following part is under preparation:
 Part 2: Measurement of the directional diffusion coefficient in a free field
iv © ISO 2004 – All rights reserved

Introduction
The degree of acoustic scattering from surfaces is very important in all aspects of room acoustics (e.g. in
concert halls, sound studios, industrial halls and reverberation chambers). Insufficient scattering may cause
strong deviations from exponential sound pressure decay. On the other hand, an approximately diffuse sound
field may be obtained with highly scattering surfaces in a room. The degree of scattering in a room can be an
important factor related to the acoustic quality of the room.
The scattering coefficient is introduced as a new concept in this part of ISO 17497. Together with the
absorption coefficient, the scattering coefficient will be useful in room acoustic calculations, simulations and
prediction models. For some time it has been known that modelling of the scattering from surfaces is very
important for obtaining reliable predictions of room acoustics. This part of ISO 17497 presents a measurement
method to quantify the scattering properties of a surface to replace formerly applied but not generally
accepted estimation methods.
The work has been coordinated with the working group of the Audio Engineering Society, AES SC-04-02 for
the Characterization of Acoustical Materials. This group emphasized the development of a measurement
method for the directional diffusion coefficient, which is different from (but related to) the random incidence
scattering coefficient. While the scattering coefficient is a rough measure that describes the degree of
scattered sound, the diffusion coefficient describes the directional uniformity of the scattering; i.e. the quality of
the diffusing surface. Therefore there is a need for both concepts and they have different applications.
INTERNATIONAL STANDARD ISO 17497-1:2004(E)

Acoustics — Sound-scattering properties of surfaces —
Part 1:
Measurement of the random-incidence scattering coefficient in
a reverberation room
1 Scope
This part of ISO 17497 specifies a method of measuring the random-incidence scattering coefficient of
surfaces as caused by surface roughness. The measurements are made in a reverberation room, either in full
scale or on a physical scale model. The measurement results can be used to describe how much the sound
reflection from a surface deviates from a specular reflection. The results obtained can be used for comparison
purposes and for design calculations with respect to room acoustics and noise control.
The method is not intended for characterizing the spatial uniformity of the scattering from a surface.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 354, Acoustics — Measurement of sound absorption in a reverberation room
ISO 9613-1, Acoustics — Attenuation of sound during propagation outdoors — Part 1: Calculation of the
absorption of sound by the atmosphere
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 354 and the following apply.
3.1
specular reflection
reflection that obeys Snell’s law, i.e. the angle of reflection is equal to the angle of incidence
NOTE Specular reflection can be obtained approximately from a plane, rigid surface with dimensions much larger
than the wavelength of the incident sound.
3.2
diffuse sound field
sound field in which the incident sound intensity on a plane surface is equally distributed over all solid angles
covering a hemisphere
3.3
scattering coefficient
s
θ
value calculated by one minus the ratio of the specularly reflected acoustic energy to the total reflected
acoustic energy
NOTE Theoretically, s can take values between 0 and 1, where 0 means a totally specularly reflecting surface, and 1
θ
means a totally scattering surface. The subscript θ may be used to indicate the angle of incidence relative to the normal of
the surface. Random incidence is understood if there is no subscript.
3.4
random-incidence scattering coefficient
s
value calculated by one minus the ratio of the specularly reflected acoustic energy to the total acoustic energy
reflected from a surface in a diffuse sound field
3.5
random-incidence absorption coefficient
α
s
value calculated by one minus the ratio of the total reflected acoustic energy to the incident acoustic energy,
on a surface in a diffuse sound field
3.6
random-incidence specular absorption coefficient
α
spec
value calculated by one minus the ratio of the specularly reflected acoustic energy to the incident acoustic
energy, on a surface in a diffuse sound field
NOTE This is the apparent absorption coefficient when the losses include the scattered as well as the absorbed
acoustic energy. α may take values in the range from α to 1.
spec s
3.7
physical scale ratio
1:N
ratio of any linear dimension in a physical scale model to the same linear dimension in full scale
NOTE The wavelength of the sound used in a scale model for acoustic measurements obeys the same physical
scale ratio. So, if the speed of sound is the same in the model as in full scale, the frequencies used for the model
measurements will be a factor of N times higher than those in full scale.
4 Principle
The general principle of the method can best be explained by looking at the effect of reflection and scattering
in the time domain. Figure 1 shows three bandpass-filtered pulses which were reflected from a corrugated
surface for different orientations of the test sample in the free field.
2 © ISO 2004 – All rights reserved

Key
p sound pressure, in pascals
t time, in milliseconds
Figure 1 — Examples of band-pass filtered impulse responses measured at three different positions
of the test sample
Obviously, the initial parts of the reflections are highly correlated. This coherent part is identical with the
specular component of the reflection. In contrast, the later parts are not in phase and depend strongly on the
specific orientation. The energy in the “tail” of the reflected pulse contains the scattered part.
The principle of the measurement method is to extract the specular energy from the reflected pulses. This is
done by synchronized (phase-locked) averaging of the impulse responses obtained for different sample
orientations.
The principle can be directly applied to measurements in the reverberation room. In addition to conventional
measurements of absorption coefficient, the (circular) sample is placed on a turntable and impulse responses
are obtained for different sample orientations. By synchronized averaging of the pressure impulse responses,
the specular components add up in phase, whereas the scattered sound interferes destructively.
Assuming statistical independence between scattered components, it can be shown (see [1]) that after
synchronized addition of n room impulse responses, the initial decay is related to the combined effects of
absorption and an apparent energy loss due to sound scattered from the sample.
5 Frequency range
The measurements should be performed in one-third-octave bands with centre frequencies covering the
frequency range from 100 Hz to 5 000 Hz. This refers to full-scale measurements. If a physical scale factor of
1:N is used, the centre frequencies should cover the frequency range from N × 100 Hz to N × 5 000 Hz.
NOTE If the scale model is filled with a gas in which the speed of sound is different from that in atmospheric air, the
measurement frequencies should be chosen in such a way that the wavelength obeys the physical scale ratio 1:N.
NOTE High frequencies may be omitted from the measurements if the attenuation in the air i
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