We live in a time of great sonic threat. Loud sounds are everywhere. People are not paying enough attention to their “acoustic ecology.”
Sound pressure is measured in decibels.
However, decibels are not equal in sound pressure at different points along the decibel scale. Each increase of 6 decibels represents a doubling in sound pressure. Thus, decibels at the low end of the scale are not the same size in sound pressure as decibels at the upper end of the scale.
The table below shows how sound pressure levels go up when increases are made from a starting level of 80 decibels.
Notice that the actual sound pressure at 116 decibels is 64 times greater than it is at 80 decibels. The point for you to understand is that at the higher end of the scale, small increases in decibels lead to huge increases in actual sound pressure delivered to your ears. The important fact is that high sound pressure levels will damage your ability to hear.
Our measurements show that peak output of iPods through the standard ear buds can reach or exceed 115 decibels with many different types of music. Sustained levels in excess of 90 decibels can readily be achieved.
Our tests have also shown that when the output of the sound source is between 80 to 84 decibels, comfortable listening levels have been reached. There is no need to blast the ears with higher sound pressure levels—the rewards are small and the risk to your hearing is simply too great.
The National Institutes of Health informs us that sound pressure levels at 85 decibels (dBA) and higher can produce permanent hearing damage. As a reference, heavy city traffic and noisy restaurants reach about 85 decibels. Normal conversation is at about 60 decibels.
Exposure times to loud sounds are important. For example, exposure to sounds at 85 decibels should not be greater than 8 hours each day. Over a period of years, with repeated lengthy exposures to sound pressures at 85 decibels, a person is likely to experience hearing loss.
When sound pressure levels reach 100 decibels (some motorcycles, snowmobiles, wood working shop) unprotected exposure should not exceed 15 minutes each day. Permanent hearing loss can occur soon at this sound level.
By the time sound pressure levels reach 110 decibels (chainsaw, rock concert, disco), an exposure of more than one minute can lead to permanent hearing loss.
A single exposure to sound pressure levels over 140 decibels (firecracker, rifle, handgun) can cause permanent damage to hearing.
The message is simple. Protect your hearing. Do not seek sounds that permanently damage hearing. The price for hearing loss is much greater than the pleasures received while listening to loud sounds.