Helmets don’t impair hearing.
A motorcyclist out on the road will hear just as well or even better with a helmet as without one, according to the U.S. Department of Transportation. Why? Because for someone without a helmet, the wind and sound of the engine are very loud, and any other important sounds must be even louder to be heard over all that noise. With a helmet on, surrounding sounds are quieter, but in equal proportions. This means that what can be heard over wind and engine noise without a helmet, can also be heard in the same way with a helmet since wind and engine noise will also be reduced. Technically speaking, the signal to noise ratio stays the same.
A recent study to assess the impact of a motorcycle helmet on vision and hearing capabilities found that helmet use neither reduced the ability of riders to see traffic nor increased the time needed to visually check for nearby traffic. Helmet use also did not make a difference in a rider’s ability to hear surrounding traffic sounds.