Reasonably accurate, inexpensive dB meter--ideas?

I didn't want to wait for the end of an auction, so I bought this one from a very fine seller who goes by the moniker "carnesto". I broke the first microphone (this appears to have been my fault, not his or the manufacturer's) and he sent me a new one--overnight arrival, no less--for FREE, and the unit now appears to be working perfectly.

Anyway, it turns out that, in the car at least, 85 dBA is rather....LOUD, although certainly not at screaming levels either. I'd like to keep my hearing relatively intact.

So now I have three MORE questions:

1) Is it true that 85 dBA is generally considered the cutoff for "safe" levels of continuous exposure during an eight hour work day (or is what I've looked up out of date)?

2) How necessary is it to buy a calibrator for one of these units? I haven't seen one for under ~150-200 bucks, I don't think.

3)And anyway, how is the calibrator calibrated; i.e., what's the reference signal?

Thanks.

Tvad,

I had seen that he'd posted a table with capacitor replacement values but I didn't know that he was selling calibrated units. Dang!

The required subtractive or additive compensatory values at each sampled frequency are readily available for the Rat Shack meter, a calibrated unit isn't absolutely required---just a little math. A search over on AudioAsylum netted results for me quickly. As to the prolonged exposure at 85 db. question, I suspect industrial safety specs err on the side of too much noise exposure. Quite some time ago, one of Stereophile's writers referred to a study done in the Andes of elderly men who had had no exposure to the ambient noise levels that pervade our modern world. The researchers were quite surprised to find that the study subjects had hearing acuity as good as teenage boys in our society! Now I suppose that single study wouldn't allow one to make the direct conclusion that noise exposure levels cause hearing damage at far lower levels than we suppose, but it gives great pause for thought I think.

"Quite some time ago, one of Stereophile's writers referred to a study done in the Andes of elderly men who had had no exposure to the ambient noise levels that pervade our modern world. The researchers were quite surprised to find that the study subjects had hearing acuity as good as teenage boys in our society!"
-Photon46

Perhaps these mountain men were better able to hear "high" notes...Sorry, that was bad.

That's interesting, and I've read about a similar study (perhaps the same one)--with similar results--recently. It raises the question of whether presbycusis is really a "normal" phenomenon, or is instead due to noise exposure pervasive in modern societies. The classic audiogram tests out only to 8000 hertz, and noise-induced hearing loss is stated to be characterized by a "noise notch" on the audiogram, generally in the mid frequency range of 3000-5000 hertz. In contrast, presbycusis is considered (to the best of my knowlege) by many if not most mainstream audiologists to be a "normal" age-related degradation of high frequency hearing acuity.

However, I suspect that YOUR contention is closer to the truth, and there is at least one company that makes a CD containing test tones from 20-20,000 hertz their specifications suggest that it is reasonably accurate, and at least one person has used it to generate an audiogram, and published his results on the net. Near the end of the posting, one person says that he thinks his hearing improved after a four month break from loud listening. That would be interesting--and potentially good news for a lot of folks--if true.