Axiom Home Page Forums General Discussion Home Theater SPL Meter Measurement

Zub, on the difference between A and C weighting. SPL meters have filters which intentionally roll off the frequency response(no "correction" necessary)at certain frequencies and at certain rates. The idea is to give a result that more closely matches what humans actually hear, since hearing ability is less for very low tones and very high tones than for the mid-range, and this difference increases as the sound level gets lower(Fletcher-Munson curves illustrate this). The A weighting roughly corresponds to hearing at very low sound levels while the C weighting corresponds at high sound levels and is usually suggested for use when calibrating audio equipment at a fairly high level. The curves and table shown on p.4 of this lab handout from Michigan Tech illustrate the differences. So, among other points, note that published "corrections" for the RS meter at very low frequencies don't in fact relate to meter inaccuracy, but the inaccuracy of our ears.

Greg, one point of interest that I noted on the Nady link is that Monster Cable has available a 9 volt alkaline battery for the meter for a mere $8.14, so maybe we should all stock up.

Interesting...Why then, did the article then suggest to use A weighting if it's lower, when we all seem to agree that C weighting will mpore accurately tell us how loud we are listening?

Thanks Greg and John.
I'll check RS again, otherwise one of Greg's links.