Sound levels

To aid my ongoing fiddling with baffles, I've bought meself one of
these http://www.maplin.co.uk/module.aspx?ModuleNo=25671&doy=24m6

However I'm a bit confuddled. It's got 'A' & 'C' weighting, & in the
instructions it says 'C' should be used for measuring things like
engines, so that's what I set it to.

Now I'm no expert, but I'm guessing 112dB at idle is a tad on the noisy
side. Better than the 117dB I was getting before fitting my latest
bodged baffles, but still not good.

The thing is it doesn't /sound/ that loud. So I changed the meter to
'A' weighting, & that gives 92dB, which seems far more accurate to my
untrained ear.

So the question is, should I be using 'A' or 'C' weighting?

 

A Weighting A standard weighting of the audible frequencies designed to reflect the response of the human ear to noise.
C Weighting A standard weighting of the audible frequencies used for the measurement of Peak Sound Pressure level.

dB(A) Decibels A weighted
dB(C) Decibels C Weighted

Most measuremens are done in dBa or DB(A. Like response curves in Hi-Fi,
hence the specification of the Race Noise Limit as 105dBA.
http://www.bristolmc.org.uk/Reference/exhaust_noise.htm

HTH

 

`A' is supposed to mimic (crudely) the response of the ear to
continuous noise. Use that.

 

It does thanks. I'll ignore the instructions & use 'A' then.

 

Cheers, 'A' it is then.