This document specifies 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.
This document is applicable to:
— the 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 test specimen section;
— the determination of the intrinsic characteristics of sound absorption of road traffic noise reducing devices in actual use under direct sound field conditions;
— the comparison of design specifications with actual performance data after the completion of the construction work;
— the verification of the long-term performance of road traffic noise reducing devices (with a repeated application of the method).
This document does not apply to:
— the 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 between 200 Hz and 5 kHz, for qualification purposes. If it is not possible to get valid measurement results over the whole frequency range indicated, the results are given in a restricted frequency range, and the reasons for the restriction(s) are clearly reported.
For indoor measurements, see Annex D.