Objective assessment on earmuff behavior in windy condition

Abstract

A low frequency noise is always heared when wearing earmuff in windy condition, the noise is more than 40 dB higher than background noise at 50 Hz and most of energy is below 200 Hz at wind speed of 3.5 m/s. An objective measurement methodology was proposed to investigate low frequency noise when wearing earmuff in windy condition. Firstly, taking vehicle wind noise generation and transmission mechanism into cabin as an example, the mechanism of low frequency noise generation inside earmuff by wind was investigated, and the sources generated by wind and paths that transmit sources into earmuff were all listed. Then dedicated experiments were designed and conducted to separate each source and path contribution, and each contribution to noise inside earmuff were calculated and analyzed quantitatively with dedicated experiment results, it is found that the turbulent pressure on outside surface of earmuff transmitted through earmuff shell is the dominant contribution. Finally, porous material is effective to eliminate turbulent pressure and was attached to outside of earmuff shell as a potential passive earmuff anti-wind solution, experiment results showed good anti-wind performance.