Reference: The ASHA Leader (Oct. 11, 2011)

The distinctive roar of a motorcycle engine is loud, but studies have revealed the biggest source of noise for motorcyclists is generated by air whooshing over their helmets.  Even at legal speeds, the sound can exceed safe levels.  Researchers in the United Kingdom placed motorcycle helmets on mannequin heads, mounted them in a wind tunnel, and turned on fans.  By placing microphones at different locations around the helmet and at  the mannequin's ear, researchers found that an area underneath the helmet and near the chin bar is a significant source of the noise that reaches rider's sensitive eardrums.  Future tests will move beyond the wind tunnel to riders on the open road.  The findings, described in the Journal of the Acoustical Society of America, may lead to quieter helmet design.  Search "hard on hearing" at www.aip.org/aip.