Audio Systems: spl measuring, db meter, information windows

Question
I wanted to measure what the spl is in my car, I have a radioshack db meter (Analog one). what settings do I use on the meter? and should I test with windows open or closed? Thanks  Elliott

Answer
It depends on what you are wanting to do with it.

Generally, use the A-Weighting and slow response for more average readings.
Generally speaking the overall level found from A weighted spectrum correlates well with subjective assessment of loudness or SPL. The C weighting curve gives equal emphasis over the normal hearing range from 31.5Hz to 8kHz.

This image illustrates the spectrums or different weighting.
http://www.prosig.com/signal-processing/weight/weight.gif
You can see that A weighting is easily the most productive when you are trying to attain accuracy.

Generally, the Fast/Slow Response switch is for resolving the reading from Peak or RMS. Remember that this Radio Shack unit is not high quality, but if used properly, it can give you some very useful information.

Windows up or down..  why not try both since you are just learning about it. You might also try exterior readings with them up and down to see how well it damps the sound with them closed.


J Mael