Driving a convertible exposes drivers and passengers to dangerous noise levels.
Driving a convertible with the top down could expose you to dangerous noise levels on a par with a building site, claims a new study. Levels as high as 100 decibels were recorded at speeds of 75mph which for long periods could lead to damage to hearing.
Even at 55mph levels were above 85dB, the equivalent to a construction site.
Road surface, other traffic, wind noise and driving speed all contributed to the cacophony.
Noise spikes – caused by passing cars, lorries and motorbikes added to the danger.
The researchers carried out tests on five cars including a Porsche, Saab, Nissan and Ford and recorded the noise levels at 55mph and 75mph.
They found that at the lower speed sound levels regularly exceeded 88dB, the equivalent of a diesel train passing or a construction site.
At the higher speed it could be the equivalent of a jet plane passing over head or a nightclub.
Exposure to noise above 85dB for prolonged periods is generally considered to damage hearing.
Not only was the mean 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 tested.
The passenger took a series of between eight to 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 convertible cars may also be exposed to additional noise when listening to the car radio.
Even for comfortable listening, the radio volume levels required while driving under the conditions assessed in this study are likely to add significantly 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 no more than minimal risk of excessive noise exposure when driving with the convertible top closed.
Dr Anthony Mikulec from the Saint Louis University School of Medicine, Missouri, 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 long duration driving at high speeds with the convertible top open will increase the driver’s risk of hearing damage.”
“In light of the results of this study, we are recommending that drivers be advised to drive with the top closed when travelling for extended periods of time at speeds exceeding 85.3 kmph (52mph).”
The study was published in the Journal of Laryngology and Otology.