ASA - ANSI/ASA S1.17 PART 1
AMERICAN NATIONAL STANDARD Microphone Windscreens – Part 1: Test Procedures for Measurements of Insertion Loss in Still Air
|Publication Date:||29 April 2014|
Part 1 of this standard describes alternative methods for determining the insertion loss of a windscreen placed around a specified stationary microphone in still air or moving slowly along a path in still air. The insertion loss is determined by measuring the sound pressure level without and with the windscreen around the microphone. The insertion loss is measured either in anechoic space or in a reverberation room. The measured insertion loss is the result of the characteristics of the windscreen including sound absorption, sound insulation and sound diffraction properties of the windscreen material, and from sound diffraction effects of the windscreen size, shape and construction details.
NOTE Although measurements of insertion loss of a windscreen in still air do not characterize the acoustical performance of the windscreen in moving air, they do provide an indication of the effect of a windscreen at wind speeds approaching zero on the level of the sound pressure at the microphone as modified by the presence of that windscreen.
This standard applies to any kind or shape of windscreen made from any kind of porous material and intended to be placed around a measurement microphone to reduce the influence of moving air on the sound pressure at the microphone, or to provide protection from dust and other particles in the air. Other windscreen properties are cited in Annex A. This standard also applies to porous "nose cones" placed around a microphone in a flow of air or other gas.
Insertion loss is measured in an anechoic room for applications where it is important to know the effect of a windscreen on a microphone's directional response as well as the effect on the acoustical sens itivity of a measurement system. Insertion loss is measured in the diffuse field of a reverberation room for applications where sound arrives at a microphone from random directions.
This standard describes methods for determining the insertion loss of a windscreen over a frequency range selected by the user as applicable to an intended measurement of the sound pressure level at a point in a sound field. The measured insertion losses may be used to classify windscreens according to their physical properties. The measured insertion losses may also be useful for estimating the sound pressure levels that would have been measured in the absence of a windscreen. Annex A provides general information about microphone windscreens.1
1 The Bibliography contains a list of references with information about the design and testing of microphone windscreens.