Acoustical Society of America - 161st Meeting Lay Language Papers
Motorcycle helmets and the frequency dependence of temporary hearing threshold shift
Dr Nigel J Holt (firstname.lastname@example.org)
Dr Michael Carley
Dr John Kennedy
Dr Ian Walker
Popular version of paper 5aPP1
Presented Friday. 27th May
161st ASA Meeting, Seattle, Washington
Most people have been to clubs, festivals and concerts. Many have fought their way to the front and ended up standing close to the stacks where it is possible to feel the breeze coming off the speakers as the band turn the volume up to 11. This level of noise exposure can have a surprisingly significant affect on your hearing in the short term. Evidence your hearing has changed is often experienced as a ringing in the ears the following morning, an experience also familiar to those who ride motorcycles. Most people are unaware that these types of exposure to noise will change their hearing sensitivity. This sort of change to our hearing is temporary – we recover over time. Repeatedly experiencing these types of sounds, particularly before fully recovering can mean that the temporary shift may develop into a permanent hearing loss.
We have measured the type of threshold shift people experience at different frequencies when exposed to noise in normal listening conditions. Wearing a helmet changes the sounds motorcyclists would otherwise be exposed to and because of this the resulting threshold shifts are at different frequencies than would otherwise be expected. We looked at the way the helmet filters sound and found that the effect was to block out certain frequencies of the sound but amplify others. After listening to noise while wearing the helmet, riders become less sensitive to frequencies amplified by the helmet, as expected. Counterintuitively, they actually experience a temporary improvement in their hearing at frequencies blocked out by the helmet.
The type of hearing protection currently available to riders is of a very basic nature, such as ear-plugs and neck-shields. It is important to note that silence is not ideal either, as portions of the sound provide important rider feedback during driving. Hearing protection for motorcycle riders needs to be tailored towards those frequencies that are most detrimental to rider safety, health and comfort. The information revealed in our research, is a first step in setting design goals for developing these noise reduction technologies.
Contacts at the ASA, Sunday 22nd May to Wednesday 25th May – Dr John Kennedy and Dr Michael Carley (Affiliation – University of Bath, England)
Contact at the ASA Thursday 26th and Friday 28th – Dr Nigel Holt (Affiliation – Bath Spa University, England)