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Is my sound level meter defective?

post #1 of 5
Thread Starter 
After some less than stellar results from the online tests at http://www.digital-recordings.com/he...-products.html, I became concerned about whether I might be doing damage to my hearing with long-term use of my headphones, so I bought a basic digital sound level meter from RadioShack. I cut a hole in a piece of cardboard to insert the "business end" of the meter into, and fixed it to the earcup of my headphones with rubber bands.

Settings are on "C" weighting, fast response.

It turns out I'm listening at between 50 and 60 dBs. Peaks in the high 50s or low 60s.

Ordinarily, this would comfort me, but to experiment, I pumped up the volume to try to get to what I've read is the "danger zone," above 80 dB. It's shockingly, painfully loud. I can't believe anyone would be able to listen to that volume over long periods of time and think that it's "normal."

Is that right? Is there something about my methodology that's off? If it helps, I'm using Grado SR-225s, directly out of my PowerBook G4's headphone jack, with iTunes as my application. My normal listening volume is to have the PowerBook's main volume at about 12% (two notches on the scale that appears when you manipulate the volume using the volume keys). The iTunes volume is set a little over halfway. My music files are replaygained with 89 dB as the target.
post #2 of 5
Well, if it's any consolation, my RadioShack meter tells me the exact same thing and I was equally surprised. Best way to measure it, though, is to cut a hole in some cardboard and then press it against the ear pieces to not let any sound pressure escape.

The OSHA (abbr?) figures which say 80dB is fine are out of date, 80dB is safe for something like 1h30m according to the latest World Health Organization consensus.

If you listen at low levels and let your ears gradually become accustomed to the low volume till it's engaging, 60dB peaks is what I'd expect to read. The RadioShack meter is used by a lot of enthusiasts, though I too am still a little skeptical.
post #3 of 5
Thread Starter 
Thanks, that's comforting. I do use the cardboard method.

I should probably not put too much stock into the online hearing test, either, seeing as that I don't own any closed headphones. I don't really know where the Grados' frequency response drops off, either.
post #4 of 5
I would not trust the cardbord method. It may give results very different from what's happening when headphones are worn by real ears.
Try your meter on normal noises. In the tube, I measured the signal annoucing the doors closing at 90 db.

BTW, use the A weighting in order to measure the impact on your ears.
A -> as we hear it (Fletcher-Mundson corrected)
C -> as a microphone hears it, between 20 and 20000 Hz.
post #5 of 5
Thread Starter 
Good points. Thanks. I confess that I don't really know the difference between A and C weighting, I was just doing what I had read elsewhere.
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