Driving a convertible with the top down at speeds exceeding 55mph may put drivers at increased risk of noise-induced hearing loss, according to new research published in the Journal of Laryngology and Otology, by Cambridge University Press from the Saint Louis University School of Medicine and The Ear Institute of Texas.
The research was carried out using five different makes and models of car. Sound level measurements in 80 per cent of the cars at 55mph with the top down had maximum sound recordings greater than 85 decibels.
Exposure to noise above 85dB for prolonged periods is not recommended according to the US National Institute of Occupational Safety and Health. The higher the noise level, the shorter the recommended exposure time.
At 75mph the average noise exposure in a convertible was 89.9dB. Not only was the noise exposure excessive with the top open, but the driver was also exposed to extreme noise ‘spikes’ while driving on the highway; for example, when driving next to a motorcycle or lorry. The study was undertaken using a sound level meter operated by a passenger in each car. The passenger took 8-10 sound level measurements at various points in the journey from the position of the driver’s left ear, at various speeds. During all data collection, the car radio was turned off, there was no conversation between occupants, air conditioning was turned off, the car horn was not used and there was no rain or other inclement weather.
Drivers of convertibles may also be exposed to additional noise when listening to the car radio. Even for comfortable listening, the radio volume required while driving with the top down are likely to add to the noise exposure level.
During the study, no excessive noise levels were recorded from any tested car driven with the top closed, meaning there is only minimal risk of excessive noise exposure when driving with the convertible top closed.
Dr A A Mikulec from the Saint Louis University School of Medicine, who oversaw the study, said: “When the convertible automobiles were driven with the top open, high levels of noise were consistently recorded. Although driving for short distances under such levels of noise exposure is unlikely to cause a significant degree of noise-induced hearing loss, our study demonstrates that driving for long durations at high speeds with the top down will increase the driver’s risk of hearing damage.”
“In light of these results, we are recommending drivers close the top when travelling for extended periods at speeds exceeding 55mph.”
•Note: The information provided does not indicate which cars were tested, and the vehicle used by us to illustrate this piece is purely illustrative and not an indication that it may cause excessive noise.