Acoustics - Determination of sound absorption coefficient and impedance in impedance tubes Method using standing wave ratio
Standards Australia
Specifies a method for the determination of the sound absorption coefficient, reflection factor and surface impedance or surface admittance of materials and objects. This Standard is technically equivalent to and has been reproduced from ISO 10534-1:1996.
RECONFIRMATION NOTICE
Technical Committee AV-004 has reviewed the content of this publication and in accordance with Standards Australia procedures for reconfirmation, it has been determined that the publication is still valid and does not require change.
Certain documents referenced in the publication may have been amended since the original date of publication. Users are advised to ensure that they are using the latest versions of such documents as appropriate, unless advised otherwise in this Reconfirmation Notice.
Approved for reconfirmation in accordance with Standards Australia procedures for reconfirmation on 20 January 2016.
Approved for reconfirmation in New Zealand on behalf of the Standards Council of New Zealand on 18 May 2016.
The following are represented on Technical Committee AV-004:
Acoustical Society of New Zealand
Association of Australian Acoustical Consultants
Australian Acoustical Society
Australian Building Codes Board
Australian Chamber of Commerce and Industry
Curtin University of Technology
Ministry of Health (NZ)
National Acoustic Laboratories
The University of Sydney
University of Auckland (New Zealand)
University of New South Wales at the Australian Defence Force Academy
This part of ISO 10534 specifies a method for the determination of the sound absorption coefficient,
reflection factor and surface impedance or surface admittance of materials and objects. The values are
determined for normal sound incidence by evaluation of the standing wave pattern of a plane wave in a
tube, which is generated by the superposition of an incident sinusoidal plane wave with the plane wave
reflected from the test object.
This method can be used for the determination of the sound absorption coefficient of sound absorbers for
normal sound incidence. It can further be used for the determination of the acoustical surface impedance or
surface admittance of sound-absorbing materials. It is well suited for parameter studies and for the design
of sound absorbers, because only small samples of the absorber material are needed.
There are some characteristic differences between this method and the measurement of sound
absorption in a reverberation room (see ISO 354).
The impedance tube method can be used for the determination of the reflection factor and also the
impedance or admittance. The sound is incident normally on the object surface. The reverberation
room method will (under idealized conditions) determine the sound absorption coefficient for
random sound incidence.
The impedance tube method relies on the existence of a plane incident sound wave and gives exact
values under this condition (measuring and mounting errors excluded). The evaluation of the sound
absorption coefficient in a reverberation room is based on a number of simplifying and approximate
assumptions concerning the sound field and the size of the absorber. Sound absorption coefficients exceeding the value 1 are therefore sometimes obtained.
The impedance tube method requires samples of the test object which are the size of the cross-sectional area of the impedance tube. The reverberation room method requires test objects which are rather large and can also be applied to test objects with pronounced structures in the lateral and/or normal directions. Measurements with such objects in the impedance tube must be interpreted with care (see 9.1).
For the computational transformation of the test results from the impedance tube method (normal incidence) to the situation of diffuse sound incidence, see annex D.
This part of ISO 10534 gives preference to numerical methods of evaluation instead of graphical methods, because computers which can perform these computations are assumed to be available. Some of the quantities in the formulae are complex. The arguments of trigonometric functions are in radians.
| Document Type | Standard |
| Status | Current |
| Publisher | Standards Australia |
| ProductNote | Reconfirmed 17/06/2016. This standard has been reconfirmed in Australia in 2016 and remains current in New Zealand. Reconfirmation Notice 17/06/2016 |
| Committee | AV-004 |
| Supersedes |
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