Windscreen insertion loss in still air
Keywords:Acoustic impedance, Attenuation, Audio acoustics, Insertion losses, Microphones, Windshields, Microphone windscreens
AbstractMicrophone windscreens are used to attenuate wind noise. However, even in still air, windscreens have an impact due to the added impedance between the source and microphone. This impedance is not accounted for when the system is checked by the use of an acoustical calibrator or when used in the field. The procedure for the characterization of the attenuation in still air has recently been addressed in ANSI S 1.17-2000 part 1. But to date, no commercial windscreens have been tested in accordance with that standard. One of the reasons may be because the precision of the procedure has not been determined, even though the results of a round robin and the results of the uncertainty determination are available. Some of the commonly used windscreens were tested in a small chamber approaching free-field conditions. The results of the tests of insertion loss from the non-standard method and those based on S1.17 are presented here. It is shown that in some cases, the use of a windscreen can easily change the measurements using Type 1 instruments to Type 2 or worse. Without knowing information about a particular windscreen, the use of a windscreen in still air, can drastically change uncertainty of measurement. In moving air conditions can be expected to be even more severe.
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