ISO 10534-2-2023 (2025) PDF

Full title and description

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. This international standard specifies the two‑microphone (transfer‑function) method using an impedance tube and frequency analysis to determine normal‑incidence sound absorption coefficients and surface impedance/admittance of acoustical materials; a corrected edition was issued in August 2025.

Abstract

The standard describes a test method using an impedance tube with two fixed microphone locations (or a traversing microphone) and a frequency analysis system to obtain the complex acoustic transfer function, from which the normal‑incidence absorption coefficient and the normal surface impedance (or admittance) are calculated. It also includes extensions for extracting intrinsic homogeneous‑material properties such as characteristic impedance, wavenumber and dynamic effective material parameters.

General information

• Status: Published (current edition published 2023; corrected version released 2025).
• Publication date: Edition 2 published October 2023 (document entry effective 06 October 2023 in national catalogs); corrected version dated August 2025.
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.140.01 — Acoustic measurements and noise control.
• Edition / version: Edition 2 (2023); corrected version (August 2025).
• Number of pages: 30 (as published by ISO).

Scope

This part of ISO 10534 specifies a laboratory method for measuring normal‑incidence acoustic quantities of sound‑absorbing materials using an impedance tube and two‑microphone transfer‑function processing. It is intended for plane‑wave frequency ranges supported by standard impedance tube diameters and is applicable to determination of normal‑incidence sound absorption coefficient, normal surface impedance/admittance and, where applicable, intrinsic acoustic material parameters. The method is complementary to reverberation‑room (diffuse‑field) methods and is aimed at research, product development and material characterization where small specimens are sufficient.

Key topics and requirements

• Use of an impedance tube with a defined sound source at one end and the test specimen mounted at the other end.
• Two fixed microphone positions (or an in‑tube traversing microphone) to measure acoustic pressures and compute the complex transfer function.
• Calculation of complex acoustic transfer function, from which the normal‑incidence absorption coefficient and surface impedance/admittance are derived.
• Requirements for instrumentation, calibration, specimen mounting and data processing to ensure repeatability and traceability.
• Guidance on limitations versus diffuse‑field (reverberation room) methods and notes on estimating diffuse incidence behavior from normal‑incidence results where applicable.

Typical use and users

Applied by acoustical test laboratories, research and development teams, materials manufacturers, quality control groups, consulting acousticians and university research groups for characterizing sound‑absorbing materials, validating material models, and supporting product design where normal‑incidence behaviour or material acoustic parameters are required. The method is especially useful when only small samples are available or when rapid parametric testing is needed.

Related standards

Key related standards include ISO 10534‑1 (Impedance tube method using standing‑wave ratio) and ISO 354 (Measurement of sound absorption in reverberation rooms — diffuse‑field method). ISO 10534‑2 is published under ISO/TC 43/SC 2, which covers acoustical measurement standards.

Keywords

Impedance tube, two‑microphone technique, transfer function, normal‑incidence sound absorption, surface impedance, admittance, acoustic material properties, characteristic impedance, wavenumber, acoustic testing.

FAQ

Q: What is this standard?

A: ISO 10534‑2:2023 is an international standard that specifies the two‑microphone (transfer‑function) impedance‑tube method for measuring normal‑incidence sound absorption coefficients and surface impedance of acoustical materials.

Q: What does it cover?

A: It covers the required test arrangement (impedance tube, sound source, microphone positions), measurement procedures, signal analysis to obtain the complex transfer function, derivation of absorption and impedance values, instrument calibration and notes on applicability and limitations compared to reverberation‑room methods.

Q: Who typically uses it?

A: Acoustical test laboratories, manufacturers of absorptive materials, R&D groups, acoustical consultants and academic researchers who need repeatable, laboratory‑scale normal‑incidence acoustic measurements.

Q: Is it current or superseded?

A: The 1998 edition of ISO 10534‑2 was withdrawn and superseded by ISO 10534‑2:2023 (Edition 2), which is the current published edition; a corrected version of the 2023 edition was issued in August 2025.

Q: Is it part of a series?

A: Yes — it is Part 2 of ISO 10534 (part 1 addresses the standing‑wave‑ratio method). The ISO 10534 series and related standards (for example ISO 354 for reverberation‑room measurements) form the core laboratory methods for measuring sound absorption.

Q: What are the key keywords?

A: Impedance tube; two‑microphone; transfer function; normal incidence; absorption coefficient; surface impedance; admittance; acoustic material properties.