> I was using batteries, but after doing additional recordings its clear th=
at the one I posted was getting interference. Here=92s a screenshot from a =
better recording: https://www.dropbox.com/s/k76hl2tuvjp3yzy/Rumble2.jpg
Charles,
Looks good to me. If you take different samples you should get different
wiggles, but the noise level is generally constant with frequency.
More theory coming up. :-(
Noise figures are usually given with a frequency weighting such as "A
weighting" which at least is consistent, but which does not represent what=
the ear hears at noise levels. The A curve uses a steep bass cut and also
falls off after 1KHz which is fine with studio recording but which simply
does not represent what the ears hear with quiet sounds as in nature
recording.
The Wiki page
https://en.wikipedia.org/wiki/A-weighting
is reasonably accurate and gives other curves but they are based on 40 phon=
s
when we are recording as low as 20phons. See the para on "Deficiencies of
A-weighting".
The original Fletcher-Munson_curves of the ear's responses are on;
https://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves
David Brinicombe
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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