EN ISO 10534-2:2001

SLOVENSKI STANDARD
01-december-2002
Akustika - Ugotavljanje koeficienta absorpcije in impedance zvoka v Kundtovi cevi
– 2. del: Metoda s prenosno funkcijo (ISO 10534-2:1998)
Acoustics - Determination of sound absorption coefficient and impedance in impedances
tubes - Part 2: Transfer-function method (ISO 10534-2:1998)
Akustik - Bestimmung des Schallabsorptionsgrades und der Impedanz in
Impedanzrohren - Teil 2: Verfahren mit Übertragungsfunktion (ISO 10534-2:1998)
Acoustique - Détermination du facteur d'absorption acoustique et de l'impédance des
tubes d'impédance - Partie 2: Méthode de la fonction de transfert (ISO 10534-2:1998)
Ta slovenski standard je istoveten z: EN ISO 10534-2:2001
ICS:
17.140.01 $NXVWLþQDPHUMHQMDLQ Acoustic measurements and
EODåHQMHKUXSDQDVSORãQR noise abatement in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 10534-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2001
ICS 17.140.01
English version
Acoustics - Determination of sound absorption coefficient and
impedance in impedances tubes - Part 2: Transfer-function
method (ISO 10534-2:1998)
Acoustique - Détermination du facteur d'absorption Bauakustik - Bestimmung des Schallabsorptionsgrades
acoustique et de l'impédance des tubes d'impédance - und der Impedanz in Impedanzrohren - Teil 2: Verfahren
Partie 2: Méthode de la fonction de transfert (ISO 10534- mit Übertragungsfunktion (ISO 10534-2:1998)
2:1998)
This European Standard was approved by CEN on 13 May 2001.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
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Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10534-2:2001 E
worldwide for CEN national Members.

Page 2
Foreword
The text of the International Standard from Technical Committee ISO/TC 43 "Acoustics" of the
International Organization for Standardization (ISO) has been taken over as an European Standard
by Technical Committee CEN/TC 126 " Acoustic properties of building products and of buildings",
the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2001, and conflicting national standards
shall be withdrawn at the latest by December 2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg,
Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of the International Standard ISO 10534-2:1998 has been approved by CEN as a European
Standard without any modification.

INTERNATIONAL ISO
STANDARD 10534-2
First edition
1998-11-15
Acoustics — Determination of sound
absorption coefficient and impedance
in impedance tubes —
Part 2:
Transfer-function method
Acoustique — Détermination du facteur d’absorption acoustique
et de l’impédance des tubes d’impédance —
Partie 2: Méthode de la fonction de transfert
A
Reference number
ISO 10534-2:1998(E)
ISO 10534-2:1998(E)
Contents Page
1 Scope . 1
2 Definitions and symbols . 1
3 Principle. 3
4 Test equipment . 3
5 Preliminary test and measurements. 7
6 Test specimen mounting . 8
7 Test procedure . 9
8 Precision. 13
9 Test report . 14
Annexes
A Preliminary measurements . 15
B Procedure for the one-microphone technique . 20
C Pressure-release termination of test sample. 21
D Theoretical background . 22
E Error sources . 24
F Determination of diffuse sound absorption coefficient a
st
of locally reacting absorbers from the results of this part
of ISO 10534 .
G Bibliography . 27
©  ISO 1998
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 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
© ISO
ISO 10534-2:1998(E)
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.
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 ISO 10534-2 was prepared by Technical Committee
ISO/TC 43, Acoustics, Subcommittee SC 2, Building acoustics.
ISO 10534 consists of the following parts, under the general title
Acoustics — Determination of sound absorption coefficient and impedance
in impedance tubes:
— Part 1: Method using standing wave ratio
— Part 2: Transfer-function method
Annnexes A to C form an integral part of this part of ISO 10534. Annexes D
to G are for information only.
iii
INTERNATIONAL STANDARD  © ISO ISO 10534-2:1998(E)
Acoustics — Determination of sound absorption coefficient
and impedance in impedance tubes —
Part 2:
Transfer-function method
1 Scope
This test method covers the use of an impedance tube, two microphone locations and a digital frequency analysis
system for the determination of the sound absorption coefficient of sound absorbers for normal sound incidence. It
can also be applied for the determination of the acoustical surface impedance or surface admittance of sound
absorbing materials. Since the impedance ratios of a sound absorptive material are related to its physical
properties, such as airflow resistance, porosity, elasticity and density, measurements described in this test method
are useful in basic research and product development.
The test method is similar to the test method specified in ISO 10534-1 in that it uses an impedance tube with a
sound source connected to one end and the test sample mounted in the tube at the other end. However, the
measurement technique is different. In this test method, plane waves are generated in a tube by a noise source,
and the decomposition of the interference field is achieved by the measurement of acoustic pressures at two fixed
locations using wall-mounted microphones or an in-tube traversing microphone, and subsequent calculation of the
complex acoustic transfer function, the normal incidence absorption and the impedance ratios of the acoustic
material. The test method is intended to provide an alternative, and generally much faster, measurement technique
than that of ISO 10534-1.
Compared with the measurement of the sound absorption in a reverberation room according to the method
specified in ISO 354, there are some characteristic differences. The reverberation room method will (under ideal
conditions) determine the sound absorption coefficient for diffuse sound incidence, and the method can be used for
testing of materials with pronounced structures in the lateral and normal directions. However, the reverberation
room method requires test specimens which are rather large, so it is not convenient for research and development
work, where only small samples of the absorber are available. The impedance tube method is limited to parametric
studies at normal incidence but requires samples of the test object which are of the same size as the cross-section
of the impedance tube. For materials that are locally reacting, diffuse incidence sound absorption coefficients can
be estimated from measurement results obtained by the impedance tube method. For transformation of the test
results from the impedance tube method (normal incidence) to diffuse sound incidence, see annex F.
2 Definitions and symbols
For the purposes of this part of ISO 10534 the following definitions apply.
2.1
sound absorption coefficient at normal incidence
a
ratio of sound power entering the surface of the test object (without return) to the incident sound power for a plane
wave at normal incidence
ISO 10534-2:1998(E) © ISO
2.2
sound pressure reflection factor at normal incidence
r
complex ratio of the amplitude of the reflected wave to that of the incident wave in the reference plane for a plane
wave at normal incidence
2.3
reference plane
cross-section of the impedance tube for which the reflection factor r or the impedance Z or the admittance G are
determined and which is usually the surface of the test object, if flat
NOTE  The reference plane is assumed to be at x = 0.
2.4
normal surface impedance
Z
ratio of the complex sound pressure p(0) to the normal component of the complex sound particle velocity v(0) at an
individual frequency in the reference plane
2.5
normal surface admittance
G
inverse of the normal surface impedance Z
2.6
wave number
k
variable defined by
k = ω /c = 2pf/c
0 0 0
where
w is the angular frequency;
f is the frequency;
c is the speed of sound.
NOTE  In general the wave number is complex, so
k = k ¢ – jk †
0 0 0
where
k ¢ is the real component (k ¢ = 2π/l );
0 0
l is the wavelength;
k † is the imaginary component which is the attenuation constant, in nepers per metre.
2.7
complex sound pressure
p
Fourier Transform of the temporal acoustic pressure
2.8
cross spectrum
S
product p ⋅p *, determined from the complex sound pressures p and p at two microphone positions
2 1 1 2
NOTE  * means the complex conjugate.
© ISO
ISO 10534-2:1998(E)
2.9
auto spectrum
S
product p ⋅p *, determined from the complex sound pressure p at microphone position one
1 1 1
NOTE  * means the complex conjugate.
2.10
transfer function
H
transfer function from microphone position one to two, defined by the complex ratio p /p = S /S or S /S , or
2 1 12 11 22 21
1/2
[(S /S )(S /S )]
12 11 22 21
2.11
calibration factor
H
c
factor used to correct for amplitude and phase mismatches between the microphones
NOTE  See 7.5.2.
3 Principle
The test sample is mounted at one end of a straight, rigid, smooth and airtight impedance tube. Plane waves are
generated in the tube by a sound source (random, pseudo-random sequence, or chirp), and the sound pressures
are measured at two locations near to the sample. The complex acoustic transfer function of the two microphone
signals is determined and used to compute the normal-incidence complex reflection factor (see annex C), the
normal-incidence absorption coefficient, and the impedance ratio of the test material.
The quantities are determined as functions of the frequency with a frequency resolution which is determined from
the sampling frequency and the record length of the digital frequency analysis system used for the measurements.
The usable frequency range depends on the width of the tube and the spacing between the microphone positions.
An extended frequency range may be obtained from the combination of measurements with different widths and
spacings.
The measurements may be performed by employing one of two techniques:
1:   two-microphone method (using two microphones in fixed locations);
2:   one-microphone method (using one microphone successively in two locations).
Technique 1 requires a pre-test or in-test correction procedure to minimize the amplitude and phase difference
characteristics between the microphones; however, it combines speed, high accuracy, and ease of
implementation. Technique 1 is recommended for general test purposes.
Technique 2 has particular signal generation and processing requirements and may require more time; however, i
...