ISO 10534-2:2023
Acoustics — Determination of acoustic properties in impedance tubes — Part 2: Two-microphone technique for normal sound absorption coefficient and normal surface impedance
Acoustics — Determination of acoustic properties in impedance tubes — Part 2: Two-microphone technique for normal sound absorption coefficient and normal surface impedance
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 32
- Дата публикации:
- 6 октября 2023 г.
- Издание:
- ISO IS 10534 edition 2 version 1
- ICS:
- 17.140.01
This test method covers the use of an impedance tube, two microphone locations and a frequency analysis system for the determination of the sound absorption coefficient of sound absorbing materials for normal incidence sound incidence. It can also be applied for the determination of the acoustical surface impedance or surface admittance of sound absorbing materials. As an extension, it can also be used to assess intrinsic properties of homogeneous acoustical materials such as their characteristic impedance, characteristic wavenumber, dynamic mass density and dynamic bulk modulus. 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 sound 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 and quantities reported in the previous paragraph. The test method is intended to provide an alternative, and generally much faster, measurement technique than that of ISO 10534-1. Normal incidence absorption coefficients coming from impedance tube measurements are not comparable with random incidence absorption coefficients measured in reverberation rooms according to ISO 354. The reverberation room method will (under ideal conditions) determine the sound absorption coefficient for diffuse sound incidence. However, the reverberation room method requires test specimens which are rather large. The impedance tube method is limited to studies at normal and plane incidence and 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 only, diffuse incidence sound absorption coefficients can be estimated from measurement results obtained by the impedance tube method (see Annex E).
Abstract
Overview
ISO 10534-2:2023 - "Acoustics - Determination of acoustic properties in impedance tubes - Part 2" - defines a standardized, two-microphone technique for measuring the normal sound absorption coefficient and normal surface impedance of sound absorbing materials using an impedance tube. The method generates plane waves in a tube, records acoustic pressures at two fixed locations, computes a complex transfer function and from that determines the reflection coefficient, absorption coefficient, and surface impedance/admittance. As an extension, the standard also supports deriving intrinsic material parameters such as characteristic impedance, characteristic wavenumber, dynamic mass density and dynamic bulk modulus.
Key technical topics and requirements
- Test configuration: impedance tube with a sound source at one end and the sample mounted at the reference plane at the other end.
- Measurement principle: decomposition of the interference field using two microphones (wall-mounted or in-tube traversing) and frequency-domain analysis to obtain the complex transfer function.
- Required equipment: impedance tube, two calibrated microphones, loudspeaker, signal generator, frequency analysis/signal processing system, and environmental sensors (thermometer, barometer, humidity).
- Signal processing methods referenced: cross- and autospectra estimates, frequency-domain deconvolution, and impulse-response techniques for transfer-function determination.
- Corrections and controls: microphone mismatch correction, selection of signal amplitude and averaging, specification of reference plane, and procedures to determine sound velocity and characteristic impedance.
- Output quantities: normal-incidence sound absorption coefficient (αn), normal-incidence surface impedance (Z) and admittance (G), reflection coefficient (r), and optionally intrinsic material properties (Annex F).
- Limitations noted: measures normal/plane incidence only and requires sample size matching the tube cross-section; values are not directly comparable with random-incidence absorption from reverberation-room tests.
Practical applications and who uses this standard
ISO 10534-2 is used by:
- Acoustic test laboratories performing routine material characterization.
- Manufacturers of porous absorbers, foams, and building products for product development and quality control.
- Acoustical consultants and building acoustics engineers assessing material performance at normal incidence.
- Research and university laboratories investigating material intrinsic properties (e.g., dynamic density, bulk modulus).
Practical uses include validating material performance for lightweight absorbers, deriving parameters for acoustic models, and providing rapid, repeatable normal-incidence absorption data when large reverberation-room specimens are impractical.
Related standards
- ISO 10534-1 - alternative impedance-tube method (one-microphone standing-wave technique).
- ISO 354 - reverberation room method for random (diffuse) incidence absorption (results are not directly comparable to ISO 10534-2).
Keywords: ISO 10534-2, impedance tube, two-microphone technique, sound absorption coefficient, normal incidence, surface impedance, acoustic measurements, characteristic impedance, dynamic mass density.
Технические детали
- Технический комитет
- ISO/TC 43/SC 2 - Building acoustics
- SKU
- ISO 10534-2:2023
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