ISO 13472-2:2010 音響学—現場での路面の吸音特性の測定—パート2：反射面のスポット法 | ページ 2

Foreword

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ISO 13472-2 was prepared by Technical Committee ISO/TC 43, Acoustics, Subcommittee SC 1, Noise.

ISO 13472 consists of the following parts, under the general title Acoustics — Measurement of sound absorption properties of road surfaces in situ:

• Part 1: Extended surface method
• Part 2: Spot method for reflective surfaces

Introduction

This part of ISO 13472 specifies a test method for measuring in situ the sound absorption coefficient of road surfaces as a function of frequency under normal incidence.

This method enables evaluation of the sound absorption characteristics of a road surface without damaging the surface. It is intended to be used to qualify the absorption characteristics of road surfaces used for vehicle and tyre testing. It may also be used during road construction, road maintenance, and other traffic noise studies. However, the field of application is limited to low absorption surfaces.

The method specified in this part of ISO 13472 is based on propagation of the test signal from the source to the road surface and back to the receiver through an impedance tube. The tube covers an area of approximately 0,008 m² and a frequency range, in one-third-octave bands, from 250 Hz to 1 600 Hz. It uses the test procedure and signal processing specified in ISO 10534-2, but because of the defined frequency range of application, the dimensions of the system are not adjustable, but fixed.

This method is primarily intended for smooth low absorption surfaces, such as those in accordance with ISO 10844. The method is not reliable if the measured sound absorption coefficient exceeds 0,15. Surfaces with values above 0,10 are not considered to be reflective.

This method is complementary to the extended surface method (ISO 13472-1 ^[5] ) that covers an area of approximately 3 m² and a frequency range, in one-third-octave bands, from 250 Hz to 4 000 Hz.

Both methods should give similar results in the frequency range from 315 Hz to 1 600 Hz, but their fields of application and therefore their accuracy differ strongly. The method described in ISO 13472-1 ^[5] has limited accuracy at small sound absorption values and is therefore unsuitable for checking compliance of surfaces with the requirements of such documents as ISO 10844, while the method specified here fails at higher sound absorption values.

Within their ranges, the methods are also applicable to acoustic materials other than road surfaces.

The measurement results of this method are comparable to the results of the impedance tube method, performed on bore cores taken from the surface in accordance with documents such as ISO 10534-1 ^[4] , ISO 10534-2 and ASTM E1050 ^[7] .

The measurement results obtained with this method are in general not comparable to the results of the reverberation room method (ISO 354 ^[1] ), because the method described in this part of ISO 13472 uses a plane progressive wave at perpendicular incidence, while the reverberation room method uses a diffuse sound field.

1 Scope

This part of ISO 13472 specifies a test method for measuring in situ the sound absorption coefficient of road surfaces for the one-third-octave-band frequencies ranging from 250 Hz to 1 600 Hz under normal incidence conditions. For special purposes, the frequency range can be changed by modifying the dimensions of the system.

The test method is intended for:

• a) determination of the sound absorption coefficient of semi-dense to dense road surfaces (and, if of interest, also the complex acoustical impedance);
• b) determination of the sound absorption properties of test tracks in accordance with standards such as ISO 10844 and test surfaces defined in national and international type approval regulations for road vehicles and vehicle tyres;
• c) verification of the compliance of the sound absorption coefficient of a road surface with design specifications or other requirements.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

3 Terms and definitions

For the purposes of this document, the following definitions apply.

Bibliography