Digital Sound & Music: Concepts, Applications, & Science, Chapter 4, last updated 6/25/2013
There are some options to configure that can make your measurements more meaningful.
One option is the response time of the meter. A fast response allows you to see level changes that
are short, such as peaks in the sound wave. A slow response shows you more of an average SPL.
Another option is the weighting of the meter. The concept of SPL weighting comes from the
equal loudness contours explained in Section 126.96.36.199. Since the frequency response of the human
hearing system changes with the SPL, a number of weighting contours are offered, each
modeling the human frequency response in with a slightly different emphasis. A-weighting has a
rather steep roll off at low frequencies. This means that the low frequencies are attenuated more
than they are in B or C weighting. B-weighting has less roll off at low frequencies. C-weighting
is almost a flat frequency response except for a little attenuation at low frequencies. The rules of
thumb are that if you’re measuring levels of 90 dBSPL or lower, A-weighting gives you the most
accurate representation of what you’re hearing. For levels between 90 dBSPL and 110 dBSPL,
B-weighting gives you the most accurate indication of what you hear. Levels in excess of 110
dBSPL should use C-weighting. If your SPL meter doesn’t have an option for B-weighting, you
should use C-weighting for all measurements higher than 90 dBSPL.
Figure 4.21 Handheld SPL meter
The other type of SPL meter is one that is part of a larger acoustic analysis system. As
described in Chapter 2, these systems can consist of a computer, audio interface, analysis
microphone, and specialized audio analysis software. When using this analysis software to make
SPL measurements, you need to calibrate the software. The issue here is that because the