Acoustics. Measurement of sound absorption properties of road surfaces in situ - Extended surface method
Acoustics. Measurement of sound absorption properties of road surfaces in situ - Extended surface method
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Acoustics. Measurement of sound absorption properties of road surfaces in situ - Extended surface method

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What is ISO 134721 - Sound absorption properties of road surfaces about?  

Noise pollution from road traffic is one of the most harmful environmental stressors in Europe. ISO 134721 discusses the sound absorption properties of road surfaces in situ. 

ISO 134721 is the first part of the ISO 13472 multi-series and describes a test method for measuring in situ the sound absorption coefficient of road surfaces as a function of frequency in the range from 250 Hz to 4 kHz. 

Normal incidence is assumed. However, the test method can be applied at oblique incidence although with some limitations. The test method is intended for the following applications: 

  • Determination of the sound absorption properties of road surfaces in actual use 
  • Comparison of sound absorption design specifications of road surfaces with actual performance data of the surface after completion of the construction work 

The complex reflection factor can also be determined by this method. 

Who is ISO 134721 - Sound absorption properties of road surfaces for? 

ISO 134721 on sound absorption properties of road surfaces is useful for:  

  • Relevant municipal / government authorities 
  • Roadway/highway authorities 
  • Project managers 
  • Builders  
  • Construction companies  
  • Civil engineers  
  • Acoustic engineers  

Why should you use ISO 134721 - Sound absorption properties of road surfaces?  

Acoustics is the science concerned with the production, control, transmission, reception, and effects of sound.  

ISO 134721 describes a test method for measuring, in situ, the sound absorption coefficient of road surfaces as a function of frequency under normal incidence. 

This method provides a means of evaluating the sound absorption characteristics of a road surface without damaging the surface. ISO 134721 is intended to be used during road construction, road maintenance, and other traffic noise studies. ISO 134721 may also be used to qualify the absorption characteristics of road surfaces used for vehicle and tyre testing. 

This method is based on free-field propagation of the test signal from the source to the road surface and back to the receiver. 

ISO 134721 contributes towards efforts for reduction of noise pollution, and improving quality of life in that aspect. 

What’s changed since the last update?  

BS ISO 134721:2022 supersedes BS ISO 134721:2002, which is withdrawn. BS ISO 134721:2022 includes some technical changes with respect to BS ISO 134721:2002. These include:  

  • Reference to ISO 18233 has been added, in order to have a standardized description of MLS and ESS signals. Two references on ESS have been added to the Bibliography 
  • Requirements of precision of ±0,005 m on the source-microphone distance have been released to ±0,01 m due to the correcting capability offered by the accurate alignment procedure in the new Annex F 
  • A procedure, taken from ISO 118192, to check the road surface dryness has been specified in 8.1 
  • Specifications of the time window have been improved 
  • Former Annex G on correction of small-time shifts has been replaced with the new Annex F, specifying an accurate alignment procedure; Annex F is now normative