scope:

This document describes a test method for measuring a quantity representative of the intrinsic characteristics of sound reflection from road noise reducing devices, the sound reflection index, and then calculate a single-number rating for sound absorption from it.

The test method is intended for the following applications:

- determination of the intrinsic characteristics of sound absorption of noise reducing devices to be installed along roads, to be measured either on typical installations alongside roads or on a relevant sample section;

- determination of the intrinsic characteristics of sound absorption of road traffic noise reducing devices in actual use under direct sound field conditions;

- comparison of design specifications with actual performance data after the completion of the construction work;

- verification of the long-term performance of road traffic noise reducing devices (with a repeated application of the method).

The test method is not intended for the following applications:

- determination of the intrinsic characteristics of sound absorption of road traffic noise reducing devices to be installed in reverberant conditions, e.g. inside tunnels or deep trenches.

Results for the sound reflection index are expressed as a function of frequency, in one-third octave bands, where possible, between 100 Hz and 5 kHz. If it is not possible to get valid measurements results over the whole frequency range indicated, the results should be given in a restricted frequency range and the reasons of the restriction(s) should be clearly reported.