Motorcycle helmets, while protecting bikers' brains, may also be  contributing to hearing loss. Scientists mapped the airflow and noise  patterns to find out why.
The distinctive roar of a Harley's engine is loud, but studies have  revealed the biggest source of noise for motorcyclists is actually  generated by air whooshing over the riders' helmets. Even at legal  speeds, the sound can exceed safe levels. 
Now, scientists have identified a key source of the rushing din.  Researchers from the University of Bath and Bath Spa University placed  motorcycles helmets atop mannequin heads, mounted them in a wind tunnel,  and turned on the fans. By placing microphones at different locations  around the helmet and at the mannequin's ear, the researchers found that  an area underneath the helmet and near the chin bar is a significant  source of the noise that reaches riders' sensitive eardrums. 
The team also investigated how helmet angle and wind speed affected the  loudness. Future tests will move beyond the wind tunnel to real-life  riders on the open road. The findings may one day be used to design quieter helmets, saving riders' ears for the enjoyment of hard biker rock, the researchers say.  
 
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