Are convertibles hazardous to your hearing?

Source: Los Angeles Times

A decibel (abbreviated dB) measures the intensity of a sound. The zero point of the decibel scale is called “near total silence.” As long as we’re living and breathing on the earth, we’re never going to experience absolute, total silence.
If you scan the increasing decibel levels of familiar sounds, the numbers may seem to rise gradually enough. But they pack more punch than their size suggests. That’s because the decibel scale grows logarithmically. A 20 dB sound (a whisper) isn’t 20 times louder than near total silence. It’s 100 times louder.

• Breathing – 10 dB
• Rustling leaves – 15 dB
• A mosquito – 20 dB
• Sitting in a library – 30 dB
• Refrigerator hum – 40 dB
• Normal conversation – 60 dB
• Street traffic – 70 dB
• Barking dog, TV, dishwasher – 75 dB
• Vacuum cleaner – 80 dB
• Telephone dial tone, garbage disposal – 85 dB
• Lawnmower, subway, “teenage” stereo – 90 dB
• Blender – 100
• Motorcycle, train, orchestra – 105
• Car horn, power saw, crying baby – 110 dB
• Rock concert, jet engine – 120 dB
• Air raid siren, cymbal crash – 130 dB
• Gunshot, firecracker – 140 dB

Dangerous sound levels

Any sound above 85 dB can cause hearing loss, depending on how long you’re exposed to the sound. You know you’re in the presence of an 85 dB sound when you need to raise your voice to be heard.
Repeated exposure to a sound level of 85 dB causes gradual hearing loss. If you spend an eight-hour day in the presence of a 90-dB sound, it can damage your ears. One minute at 100 dB causes permanent hearing loss. Any exposure to a 140 dB sound causes immediate damage.
This does get a bit gruesome, I admit, but in the interests of completeness and curiousity: Pain begins at 120 dB. At 150 dB, the chest wall begins to vibrate. At 160 dB, the ear drum will break instantly. At 180 dB, the tissues of the ear will die.
The loudest possible sound is 194 dB. You might not think there would be a loudest possible sound, but it has to do with atmospheric pressure (at sea level) and how sound waves travel in air. 194 dB breaks the bones in the ear.

Driving a convertible with the top (and the windows) down

So what’s the decibel level of driving in a convertible with the top down? Turns out the average level is between 87 and 89 dB.
A recent study in the UK tested a variety of cars (ranging in price from $22,000 to $238,000, BTW) at speeds of 50, 60, and 70 mph. The highest dB level recorded was 97.
The noise when driving a convertible comes from the tires on the surface of the road, other cars and trucks in surrounding traffic, the car’s engine and exhaust, and the wind created by the movement of the car.
If you roll the windows up, even if you keep the top down, this provides some protection against wind and road sounds. The noise level decreases to somewhere between 82 and 84 dB.
It’s not just convertibles that exceed safe noise levels. Driving any car with all the windows rolled down produced a noise level above the 85 dB threshold for hearing loss.
The BBC offered this advice:

Experts warned that the damage to hearing builds up gradually and the effects may not be noticed until years later, when it is too late.
Dr Mark Downs, of the Royal National Institute for Deaf People, said: “Noise-induced hearing loss is frequently preventable.
“Regular exposure to noise levels of 88-90 decibels when driving a convertible for several hours a day can lead to permanent hearing loss over time.
“By winding up the windows or wearing basic ear protection, such as earplugs, drivers of convertibles can still enjoy driving whilst protecting their hearing.”

Are electric cars too quiet?

Curiously, at the other end of the spectrum, there’s concern that hybrid cars are too quiet. This poses a danger to children, pedestrians, the blind, and any other living thing who wants to get out of the way of an approaching car.
Laboratory tests indicate we can hear an approaching gas-powered car at 28 feet. We don’t hear a hybrid (operating in silent battery mode) until it’s seven feet away. A congressional bill, The Pedestrian Safety Enhancement Act of 2009, would require a federal safety standard to protect pedestrians from cars that are super-quiet.
Hybrid auto companies are working with special-effects technicians from the film industry to design cool custom sounds for hybrids. According to Paul Scott, VP of an advocacy group called Plug In America:

“Quiet cars need to stay quiet — we worked so hard to make them that way,” he said. “It’s the driver’s responsibility not to hit somebody.”
Mr. Scott has already warmed up to the idea of a car ring tone.
“It should be a manually operated noisemaker, a button on the steering wheel triggering a recording of your choice,” he said. “It could play ‘In-a-Gadda-Da-Vida,’ or anything you like.”

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