How does loud or unending noise damage hearing?

Basically, a sound wave vibrates the eardrum and then passes to the cochlea, which contains rows of microscopic hair cells bathed in fluid. These hair cells move with the sound and send signals through the auditory nerve to the brain, which interprets the sound.

Noise that’s too loud or long-lasting destroys the hair cells, causing hearing loss or partial deafness. But that’s not all.

Recent studies show that noise also severs connections between nerves and brain, a likely cause of such abnormalities as the inability to separate background from foreground sound. People typically notice the problem when conversing in a crowded restaurant.

The mechanisms of tinnitus remain a mystery. One study used electrodes to measure the brain activity of a 50-yearold man with tinnitus and hearing loss. The patient had been a recreational gun user in his younger days.

The effects of the tinnitus permeated many parts of his brain, while a matching tone activated only the part of the brain that processes hearing. In other words, the “noise” of tinnitus affects the brain far differently than a similar real noise does. That may explain why tinnitus is so distressing, said Phillip Gander, a postdoctoral research scholar at the University of Iowa, who is the study’s co-author.

Noise can also activate pain fibres in the inner ear. These fibres, which have been identified in mice though not yet in humans, probably explain the pain that occurs with an intensely loud noise as well as pain that can linger after the noise stops, said Jaime García-Añoveros, an associate professor at Northwestern University in the US and the senior author of a new study on “auditory nociception” or, in lay terms, “noise-induced pain”.

Another unexplained symptom – the feeling of aural fullness or pressure in the ear canal, not unlike the pressure felt during an airplane descent – may be caused WHETHER noise will harm your hearing depends on a combination of factors such as volume, exposure time, frequency and individual susceptibility.

A single episode of very loud noise can do damage, but so can not-so-loud noise that extends over a long time.

Decibel readings offer the most convenient way of measuring noise exposure. For context: ordinary conversation between two people is about 60 decibels.

At the other end of the spectrum, the pain threshold – where damage can be done quickly and where you’d be inclined to cover your ears – generally starts at around 120 decibels, researchers say.

Here are approximate decibel values for some things that are louder than you might think. Baby rattle Food blender Lawnmower Hand drill Football game High-speed hand dryer Hairdryer Car race Referee’s whistle 81 88 95 98 Up to 99 0-100 80-95 104-109 104-116

If you’re interested in monitoring how much noise you’re being exposed to, there are some free or inexpensive noise-measuring apps available both for iPhones (among them Decibel Ultra, NoiSee, dB Meter, SPLnFFT Noise Meter and Noise Hunter ) and Android phones (including Sound Meter, Noise Meter and deciBel). – The Washington Post