gda@creare.uucp (gda) (07/08/85)
The mention of possible hearing loss from "digital ready" headphones
prompted me to mention an editorial appearing in "Sound and Vibration", May,
1985. It discusses some experiments with "Walkman" systems, trying to
determine if they are dangerous to our hearing. The main points were
1) Early work, done with dummy heads, showed that dangerous levels were
possible, but failed to point out that at those levels the distortion was so
bad that no one would want to listen to it.
2) Experiments measuring the actual sound levels heard by people using these
players in normal situations (indoor, outdoor, on-the-job) showed pretty
safe levels (even for college students!).
So by and large, the "Walkman" was judged safe for use (the article goes on
to discuss whether or not the open-air type headphones provide any PROTECTION
from environmental noise, like in a factory; they don't). I was certainly
glad to hear this, since I have grown to depend on my Walkman; it gets me
through those late hours of computer hacking. (I've contended that if
Admiral Bird had had a Walkman he would have made the pole on the first
attempt.)
By the way, when I was working at AR, all we did to make our speakers
digital ready was to stick a label on them saying "Digital Ready". We'd
been pumping digitally generated signals through them for years.
Gray Abbott
Creare Inc.
Hanover, NH
{...dartvax!creare!gda}hrs@homxb.UUCP (H.SILBIGER) (07/16/85)
The OSHA Federal regulations on hearing protection has the following limits on exposure to noise: Sound Pressure Maximum Level, dB(20uPa) Time, hrs 85 hearing monitoring required 90 8 95 4 100 2 105 1 110 .5 115 .25 Levels over 115 dB are not permitted. These levels apply to sound fields. Because of characteristics of the ear canal, an additional 3 dB can be allowed when using earphones of the closed type. It is possible to get a hearing loss from listening to music at excessive levels over earphones