dB-meters, A-weighting and Safe Noise Levels...?

Hi to all,

Some of you might know that the dB scale is a relative scale, it is alway compared to some kind of reference level. If we consider the normal pure tone hearing test, 0 dB would simply mean the average hearing threshold of a healthy population. Since the sensitivity of human hearing greatly varies with frequency I can only imagine that the pure tone audiometry is corrected for that. (A-weighted). Correct?

I used a dB-meter in my car to check the noise levels. Overall the noise levels (at highway speeds) is under 75 (near the driver window) dB. But, the dB meter used A weighted filtering. If I used a flat weighted filter I would read some where near 95 dB. For comparison, if I use the dB meter in our sound insulated room it read about 26 dB(A) or 46 dB(flat). I am either easily below the 80 dB safety limit of 8 hours per day or way above it.

Now for the question...the industry safety limit of 80 dB A-weighted or flat? I guess it is alway A-weighted, but I am not sure.

I also learned that smartphone app dB meters are useless.

 

My understanding is dB(a) is what is used for industry and any thing else in regards to human ear and sound levels.

 

Bump to this question. I want to know too please.