Source: Tom's Guide US | Keywords: decibels, noise, canceling | Themes: Audio/Video Players
3. Damage Sets In
Most sources agree that 85 dB is the threshold for safe, prolonged noise levels. The possibility of hearing damage obviously relates directly to the volume of noise and how long one is exposed to it. A ballpark rundown looks something like the following. These numbers come from Occupational Safety and Health Administration Regulation 1910.95 on occupational noise exposure.
- 90 dB – can damage with 8 hours exposure per day
- 100 dB – can damage with 2 hours exposure per day
- 110 dB – can damage with 30 minutes exposure per day
- 120 dB – can damage with 7.5 minutes exposure per day
By the time we get to 130 dB, you’re looking at an damage-causing exposure of less time than the length one song. Of course, these numbers aren’t absolute, but you can get a better understanding of what’s going on if you know exactly what is being damaged. Within the inner ear sits your cochlea, a snail-shaped affair that sports a fluid-filled interior surface blanketed with tiny hair-like structures. When sound waves enter through your ear and the auditory canal, the waves are transmitted through a series of structures to the cochlea. The sound waves vibrate the little hairs, and these vibrations are converted into impulses sent to the brain via the cochlear nerve. Trouble arises when the hairs are vibrated excessively, shocking and damaging the structures. This is why you have hearing temporary hearing loss or ringing in your ears after exposure to very loud sounds. You’ve damaged the cochlear structures, and this is how the body informs you of the damage.
Like most injuries to your body, this will heal, but we all know what happens to repeated injury to the same body part—eventually it doesn’t heal completely. Imagine walking on grass. You can walk on it many times, and, given enough time between being trampled, the grass will spring back and be fine. But with enough traffic, it will start to become sparse. With even more traffic, or with fewer times being trampled by a much heavier object, such as a tractor, the damaged grass may die altogether. This is deafness. So while a single session of cranked up rock may not have crushed my hearing, half a dozen teen years of headphones and cranked up car stereos just might have...at least a bit.
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One word: Google.
Gosh, we're not the general public... we're nerds
correction, physical pain doesn't set in at 130db, feeling sets in at about 130 db, so that bass that you feel thumping is above 130db, but since volume is a function of decibels and frequency it is very quiet. but children wailing is very high pitched so them at 80 db is significantly louder than the bass in your car. if you want to learn more than just do some more googling around. try searching "volume"
A clarification on ANC theory. There is no "anti-noise" generated. Ambient sounds strike the speaker cone moving it. Essentially the ANC signal applied to the diaphragm resists this motion of the cone, holding it still. Without movement the sound energy is dissipated as heat on the back surface of the cone. It is not canceled out in the classic sense, the compression and rarefaction of sound waves are mechanically destroyed.
One more really simple thing to add here. Put some really high-quality foam earplugs in your ear canal AND use your ANC headphones. This is what I do when I fly (Bose QC2's and custom-fit plugs). You've got to have enough sound without distortion in your headphones to overcome the attenuation of the plugs but for the most part their response curve is flat (if not a bit high on the low end). So your tinny-sounding earphones are actually going to have a bit more bass overall.
I've also been known to wear my Shure earbuds under my QC2's but they stick out far enough that I have to be careful not to touch them against the inside of the headphones. The nice bit is that even sitting in the back of an MD-80 I've only got to put my iPod at about 25% volume to hear every detail.
Shures with QC2 sounds like Heaven...assuming Heaven is a very quiet place. :-)
Regarding joeman42's comment, first, I'm going to say that I am definitely not a sound engineer nor any kind of other acoustic specialist, so the depth of my understanding may need improvement. However, the description I gave of ANC fits every description of the technology I've been exposed to over the years. For example, check this paper: http://doctord.dyndns.org:8000/Pubs/POTENT.htm, which describes the ANC process like so: "the noise is modeled to produce an anti-noise waveform at the output speaker." Given this guy's title as Vice President of R&D for Noise Cancellation Technologies, Inc. and the fact that this paper appeared in an IEEE publication, I'm pretty confident of the source.
Another very entertaining article from you.
“(Once again, you can tell something about the quality of a site’s content by the frequency of typos and errors in its text.)”
You might want to change that line before someone of bestofmedia knocks on your door and gives you a kick in the nuts when you open.
Another very entertaining article from you.“(Once again, you can tell something about the quality of a site’s content by the frequency of typos and errors in its text.)”You might want to change that line before someone of bestofmedia knocks on your door and gives you a kick in the nuts when you open.
Yeah, I can add that to the list of reasons I've given them. ;-) But really, you can tell the difference between a rushed schedule and borderline illiteracy or outright disregard for quality. If I've got to take one in the giggleberries for saying that Web sites in general need better quality control, so be it, but I think Bestof has a good crew that does good work. I'd rather have a few typos and solid reporting from people who care about the readers' best interests than a lot of the over-polished, under-thought dreck common in the field.
Thanks for the kind words.
Interesting article
I have hearing loss. I was born since birth, and therefore, I can't use headphones or go to rock concerts, lest I risk damage to my ears. I have never used an i Pod for more than a few minutes, and I'm glad.
I'm 15 years old, and I estimate that by the time I'm 40, my generation will have worse hearing than me. I'll be laughing "I HAD hearing loss BEFORE it was POPULAR!"
I should hope so.