ISO 10534-2-2023 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 a two‑microphone transfer‑function technique using an impedance tube and frequency analysis to determine normal‑incidence sound absorption coefficients and surface impedance/admittance of sound‑absorbing materials; it also provides procedures to derive intrinsic acoustical properties (characteristic impedance, wavenumber, dynamic density and bulk modulus) where applicable.

Abstract

The test method uses an impedance tube with a sound source at one end and the test specimen mounted at the other, measuring acoustic pressure at two fixed positions to calculate the complex transfer function and derive the normal‑incidence absorption coefficient and normal surface impedance (or admittance). The method is presented as a faster alternative to the standing‑wave ratio technique (ISO 10534‑1) and includes notes on limitations (normal/plane incidence only) and extensions to infer intrinsic homogeneous material properties.

General information

• Status: Published (International Standard).
• Publication date: 6 October 2023 (edition 2).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.140.01 (Acoustic measurements and noise abatement — general).
• Edition / version: Edition 2 (2023).
• Number of pages: 30 (ISO published document).

Scope

Specifies a laboratory method using an impedance tube and two microphones (fixed positions or wall‑mounted/traversing microphone) with digital frequency analysis to determine the normal‑incidence sound absorption coefficient and the normal surface impedance/admittance of acoustic materials. The procedure covers measurement set‑up, calibration, data acquisition and calculation of the complex transfer function and derived parameters, and provides guidance on sample mounting, frequency range limitations, uncertainty considerations and optional derivation of intrinsic homogeneous material properties. The method applies to plane‑wave conditions (normal incidence) and explicitly notes that results are not directly comparable with random‑incidence (diffuse field) absorption measured in reverberation rooms (ISO 354).

Key topics and requirements

• Impedance‑tube measurement using two microphones and transfer‑function analysis.
• Determination of normal‑incidence sound absorption coefficient and normal surface impedance/admittance.
• Instrumentation and calibration requirements: microphone positions, tube terminations, sound source, and frequency analysis system.
• Calculation of complex acoustic transfer function and derivation of reflection coefficient, absorption coefficient and related intrinsic properties (characteristic impedance, wavenumber, dynamic mass density, dynamic bulk modulus) where applicable.
• Specimen preparation and mounting rules (sample size matched to tube cross‑section, edge sealing or supporting grid as required).
• Limitations and interpretation guidance — normal incidence only; conversion or estimation to diffuse incidence for locally reacting materials is discussed (informative annex).

Typical use and users

Used by acoustical testing laboratories, material manufacturers (acoustic foams, fibrous absorbers, porous materials, perforated panels), R&D groups, universities and building acoustics consultants for product development, quality control, specification verification and research into material acoustic properties. Also used to validate impedance‑tube instrumentation and to produce data for acoustic simulation and modelling workflows.

Related standards

Closely related standards and documents include ISO 10534‑1 (Method using standing‑wave ratio — the alternative impedance‑tube technique), ISO 354 (measurement of sound absorption in reverberation rooms — diffuse incidence comparison), and common laboratory/industry references such as ASTM E1050 / ASTM E2611 for impedance‑tube procedures. The previous edition ISO 10534‑2:1998 has been withdrawn and replaced by ISO 10534‑2:2023. National/adopted variants (EN ISO, BS EN, ONORM, etc.) align with this edition.

Keywords

acoustics; impedance tube; sound absorption coefficient; normal incidence; surface impedance; transfer function; two‑microphone technique; acoustic testing; material properties; ISO 10534.

FAQ

Q: What is this standard?

A: ISO 10534‑2:2023 is an international laboratory test method that specifies the two‑microphone transfer‑function technique in an impedance tube to measure the normal‑incidence sound absorption coefficient and normal surface impedance of materials.

Q: What does it cover?

A: It covers test equipment and set‑up, microphone positions and calibration, data acquisition and frequency analysis, calculation of complex transfer function, derivation of reflection and absorption coefficients, reporting requirements, specimen mounting and limitations (normal incidence only). It also includes guidance to obtain intrinsic homogeneous material properties where applicable.

Q: Who typically uses it?

A: Accredited acoustical laboratories, manufacturers of acoustic materials, researchers, product development and quality‑control teams, and consultants performing acoustic characterisation of materials and small specimens for engineering or regulatory purposes.

Q: Is it current or superseded?

A: Current. ISO 10534‑2:2023 (edition 2) was published on 6 October 2023 and replaces ISO 10534‑2:1998, which was withdrawn on the date the new edition was published. 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 the ISO 10534 series (Impedance‑tube methods). Part 1 (ISO 10534‑1:1996) describes the standing‑wave‑ratio method; both parts cover complementary impedance‑tube techniques for normal‑incidence measurements.

Q: What are the key keywords?

A: Impedance tube, two‑microphone transfer function, normal incidence, sound absorption coefficient, surface impedance, acoustic material testing, ISO 10534, acoustic measurements.