ISO 13472-1:2022

Overview

ISO 13472-1:2022 - "Acoustics - Measurement of sound absorption properties of road surfaces in situ - Part 1: Extended surface method" specifies an in‑situ test method to determine the sound absorption coefficient of road surfaces (and related materials) as a function of frequency. The method covers one‑third‑octave bands from 250 Hz to 4 kHz, assumes normal incidence (with oblique-incidence limitations addressed in Annex F), and can also determine the complex reflection factor. Measurements are based on free‑field propagation over an area of roughly 3 m and use time‑domain separation of direct and reflected signals.

Key topics and technical requirements

• Measurement range: 250 Hz to 4 kHz (one‑third‑octave bands).
• Geometry: Normal incidence assumed; oblique incidence possible with corrections (see Annex F).
• Test principle: Measure overall impulse response (direct + reflected); separate responses in time domain, compute transfer functions, and obtain reflection/power absorption metrics.
• Test system components: sound source, loudspeaker, signal generator (MLS/ESS referenced in ISO 18233), microphone, and data acquisition compliant with IEC 61672‑1.
• Signal processing: temporal separation, Fourier transform to obtain transfer functions, and correction for geometrical spreading (factor K).
• Positioning and site requirements: controlled maximum sampled area (≈3 m), careful alignment of source and microphone, avoidance of parasitic reflections, and control of background noise and meteorological conditions (wind, temperature). Road surface dryness check is specified.
• Uncertainty: standard uncertainty is limited to about 0.05.
• Documentation: procedures for calibration, sampling frequency, measurement uncertainty, and reporting are specified; example reports and correction procedures are included (Annexes A–F).

Applications

• Verification of sound absorption properties of road surfaces in actual use.
• Comparison of as‑built surface acoustic performance against design specifications.
• Support for traffic noise studies, noise mitigation design, and pavement acoustics research.
• Qualification of surfaces for vehicle and tyre testing.
• Non‑destructive field alternative to impedance‑tube testing on cores; results comparable with impedance tube methods (ISO 10534 series) but generally not with reverberation room (ISO 354) due to differing sound fields.

Who should use this standard

• Acoustic and environmental engineers
• Road authorities and pavement designers
• Test laboratories and consultants performing in‑situ acoustic verification
• Researchers in traffic noise and pavement acoustics
• Manufacturers of low‑noise pavement materials

Related standards

• ISO 13472‑2 (Spot method / tube method)
• ISO 10534‑1 / ISO 10534‑2 (impedance tube methods)
• IEC 61672‑1 (sound level meters)
• ISO 18233 (MLS and ESS signal descriptions)

Keywords: ISO 13472-1:2022, sound absorption coefficient, road surfaces in situ, extended surface method, acoustics, traffic noise, reflection factor, pavement acoustics.