ROOF OPEN
About 85 to 90 dB
With the top open, mean noise at the driver's ear ran from 85.3 dB at 88.5 km/h (55 mph) to 89.9 dB at 120.7 km/h (75 mph).
Check a journey
+14.6 dBroof down, at most
- Roof up on long fast runs
- Do not race the wind with the radio
- Time adds up
- Open-top fun, hearing intact
Researchers drove five convertibles with the roof up and down and measured noise at the driver's ear. With the roof open, every speed they tested reached the levels noise guidance treats with caution.
Updated
THE SHORT ANSWER
Open roof, fast road,
loud cabin.
One study, five cars,
three motorway speeds.
ROOF CLOSED
The quiet option
Closing the roof took levels down to about 75 dB. Opening it added an average of 12.4 to 14.6 dB at the speeds tested.
See the numbers
THE RADIO
Turning it up adds more
The researchers turned the radio off to measure. They noted that radio loud enough to hear over the wind is likely to add significantly to exposure.
What to doCHECK A JOURNEY
How loud is
your seat?
Pick a driving situation from the study to see the measured level at the driver's ear. The bar shows how it sits against the 85 dB guideline the researchers used.
Based on Mikulec and colleagues, Journal of Laryngology and Otology (2011), five convertibles, radio and air conditioning off. General information, not medical advice.
TWO NUMBERS WORTH KNOWING
A few decibels
go a long way.
One number from the convertible study,
one from WHO safe listening advice.
12.4–14.6 dB
Extra noise from opening the roof
Across the tested speeds, opening the convertible top raised noise exposure by an average of 12.4 to 14.6 dB at the driver's position.
ROOF DOWN · J LARYNGOL OTOL
4 hours
Safe weekly time at 90 dB
WHO says a sound level of 80 dB is safe for up to 40 hours a week, but at 90 dB the safe listening time falls to four hours a week.
SAFE LISTENING · WHO
For comparison, WHO lists heavy traffic heard inside a car at about 85 dB. In British workplaces, HSE rules require employers to act at 80 dB(A) and provide hearing protection at 85 dB(A).
FOUR HABITS FOR OPEN-TOP DRIVING
Enjoy the sky,
mind the ears.
None of these spoils the fun. They are about the long, fast stretches where the study found the noise builds up.
Roof up for long fast runs
The study concluded that driving with the top open above 88.5 km/h (55 mph) may exceed recommended limits, especially for prolonged periods.
Save the open roof for slower roads
Noise rose with speed, so the open-top stretches are gentlest at lower speeds.
Do not race the wind with the radio
Music turned up to beat wind noise adds to exposure. WHO suggests keeping device volume to no more than 60% of maximum.
Count the hours, not just the trip
Risk rises with level and time. At 90 dB, WHO's safe weekly allowance is four hours.
HOW THEY MEASURED
Radio off,
ear-level readings.
A passenger held a sound level meter at the driver's left ear and took eight to ten readings per journey. The radio, air conditioning, horn and conversation were all off, and no tests ran in rain.
Five convertibles were tested at 88.5, 104.6 and 120.7 km/h with the roof both closed and open. The findings were published in the Journal of Laryngology and Otology by researchers from Saint Louis University and the Ear Institute of Texas.
Questions
Questions people ask
How loud is a convertible with the roof down?
In the study of five cars, mean noise at the driver's ear was 85.3 dB at 88.5 km/h (55 mph) and 89.9 dB at 120.7 km/h (75 mph) with the top open.
Is it much quieter with the roof up?
Yes. With the roof in place the level was about 75 dB, and opening it added an average of 12.4 to 14.6 dB at the speeds tested.
Why does 85 dB matter?
The Hearing Review's summary of the study notes that the US National Institute for Occupational Safety and Health does not recommend prolonged exposure above 85 dB. In Britain, HSE requires employers to provide hearing protection at 85 dB(A) daily or weekly average exposure.
Does a few dB really make a difference?
Yes. WHO says 80 dB is safe for up to 40 hours a week, while at 90 dB the safe time drops to four hours a week.
What does the NHS suggest for protecting hearing?
The NHS advises wearing ear protection around loud noise and not listening to music too loudly, with the volume just high enough to hear comfortably.
Where the facts come from
- Journal of Laryngology and Otology: Noise exposure in convertible automobiles (abstract)
- The Hearing Review: Another risk to hearing, driving a convertible (2011)
- The Naked Scientists: Going topless harms hearing (2011)
- WHO: Deafness and hearing loss, safe listening
- HSE: Control of Noise at Work Regulations 2005
- NHS: Hearing loss