Department of Mechanical Engineering, University of Bath, Bath, BA2 7AY, United Kingdom.
J Acoust Soc Am. 2011 Sep;130(3):1164-72. doi: 10.1121/1.3621097.
The prevalence of noise in the riding of motorcycles has been a source of concern to both riders and researchers in recent times. Detailed flow field information will allow insight into the flow mechanisms responsible for the production of sound within motorcycle helmets. Flow field surveys of this nature are not found in the available literature which has tended to focus on sound pressure levels at ear as these are of interest for noise exposure legislation. A detailed flow survey of a commercial motorcycle helmet has been carried out in combination with surface pressure measurements and at ear acoustics. Three potential noise source regions are investigated, namely, the helmet wake, the surface boundary layer and the cavity under the helmet at the chin bar. Extensive information is provided on the structure of the helmet wake including its frequency content. While the wake and boundary layer flows showed negligible contributions to at-ear sound the cavity region around the chin bar was identified as a key noise source. The contribution of the cavity region was investigated as a function of flow speed and helmet angle both of which are shown to be key factors governing the sound produced by this region.
近年来，摩托车骑行中的噪声问题一直引起骑手和研究人员的关注。详细的流场信息可以深入了解头盔内产生声音的流动机制。这种性质的流场调查在现有文献中并不常见，因为文献往往侧重于耳内声压级，因为这些对噪声暴露法规很重要。对一款商用摩托车头盔进行了详细的流场调查，结合表面压力测量和耳内声学进行了研究。研究了三个潜在的噪声源区域，即头盔尾流、表面边界层和头盔下巴下的腔。头盔尾流的结构包括其频率内容都提供了大量信息。虽然尾流和边界层流对耳内声音的贡献可以忽略不计，但下巴周围的腔区域被确定为一个关键的噪声源。研究了腔区域随流速和头盔角度的变化，这两个因素都被证明是该区域产生声音的关键因素。
