||Microphone Windscreen Performance.
Hosier, Robert N. ;
Donavan, Paul R. ;
||National Engineering Lab. (NBS), Washington, DC. Acoustical Engineering Div.;Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.
Noise reduction ;
Insertion loss ;
Polyester resins ;
||Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy.
||Measurements were made of the wind-induced noise and acoustic insertion loss of ten microphone windscreens. Eight of these were reticulated polyester spheres of varying porosity. The other two were the metal cage type typically used in long term outdoor noise monitoring. The measurements were made under laboratory conditions for normal and grazing flow incidence at wind speeds up to 14 m/sec. The data show that the windscreens are very different in the amount of wind-induced noise reduction they provide, with some achieving more than 25 dB. In general the foam windscreens provided more wind-induced noise reduction than the cage windscreens; however, the cylindrical cage windscreen performed better than any of the foam windscreens for normal flow incidence. The insertion loss measurements proved difficult to make because of the small insertion losses encountered. However, data for grazing flow and normal acoustic incidence show no strong velocity dependence for any of the windscreens tested. Examination of the wind-induced noise spectra provided significant insight into the noise generating mechanisms associated with flow around a porous sphere. Effects of inflow turbulence, self-generated turbulence, mean flow, flow through the sphere, and flow incidence angle were identified. Test results are provided in the form of curves and tables for easy use in evaluating potential wind noise levels in outdoor measurements.
||Sponsored in part by Environmental Protection Agency, Washington, DC. Office of Noise Abatement and Control.
|NTIS Title Notes
|PUB Date Free Form
||17B; 45C; 86V
||PC A05/MF A01