As many know but some don’t, OSHA safety guidelines for noise levels are based on dBA to account for the change in human hearing sensitivity at different frequencies. I believe dBA was a poor choice, because it is unrepresentative of the actual sound intensity in the room. (The intensity at 40 Hz must be about 40 dB higher than at 1 KHz in order to register at the same level with dBA weighting, and about 50 dB higher at 20 Hz. Consequently, I consider dBZ (no frequency weighting) to be a much more accurate representation of the overall sound intensity reaching one’s tympanic membrane and, therefore, the level of stress (or trauma) to the auditory system, regardless of frequency and how “loud” it is perceived to be.
I have always used dBZ when measuring the sound intensity in my own space, but the other day while listening at what felt like a pretty good clip, I decided to compare the two different weightings with the same selection. As expected, the average sound level according to dBA was about 15 dB lower than without frequency-based weighting (dBZ). What was unexpected was that the reported dynamic range was also significantly reduced with dBA weighting. Compare the Lmax – Lmin differences in the two readouts below. Same selection, same actual volume, same settings on all of my equipment, yet the reported dynamic range is 10.7 dB less with A-weighting.
This brings up an interesting question. Presumably, when people cite the dynamic range of certain music releases, they are basing their numbers on unweighted measurements, which I consider to be correct, but I am unsure. They generally don't specify, and some may not even realize that there will be significant a difference. Are they using frequency weighting for those numbers? Some are, but some aren't?
I have always used dBZ when measuring the sound intensity in my own space, but the other day while listening at what felt like a pretty good clip, I decided to compare the two different weightings with the same selection. As expected, the average sound level according to dBA was about 15 dB lower than without frequency-based weighting (dBZ). What was unexpected was that the reported dynamic range was also significantly reduced with dBA weighting. Compare the Lmax – Lmin differences in the two readouts below. Same selection, same actual volume, same settings on all of my equipment, yet the reported dynamic range is 10.7 dB less with A-weighting.


This brings up an interesting question. Presumably, when people cite the dynamic range of certain music releases, they are basing their numbers on unweighted measurements, which I consider to be correct, but I am unsure. They generally don't specify, and some may not even realize that there will be significant a difference. Are they using frequency weighting for those numbers? Some are, but some aren't?