Hi Peter,
This is how your test file looks in Audition's spectral view. I don't see t=
he harmonics you noted in the right channel. Perhaps it's a quirk in Audaci=
ty. Do you have access to another spectrum renderer to try the file on?
Ben
--- In Peter Shute <> wrote:
>
> Yesterday morning I made a 20 minute recording at the local wetlands with=
my new SASS array (4 x EM172's in a Rob Danielson style wooden structure, =
half finished - no nose baffle or internal baffling). I also made a recordi=
ng using the Sony PCM M10's internal mics for comparison.
>
> When I loaded into Audacity and displayed the spectrogram, I see lots of =
bands on the right channel, about 400Hz apart, to 20kHz and beyond. I can'=
t see any sign of them in the left channel, and I can't believe this thing =
has such good separation that it could be environmental. I can't hear anyth=
ing odd, but with my hearing, that doesn't mean much.
>
> I also see no sign of it in the recording using the internal mics.
>
> So it must be generated in the mic circuitry? I just made another test re=
cording with it on the table here beside me, and I see no sign of the bands=
on that recording either.
>
> So maybe it picked up some interference with it's unshielded wiring? Mayb=
e, but would that look like this? And I was at least a kilometre from the n=
earest powerlines. The site is an old saltworks, so there may have been som=
e pumps running a bit closer than that. The lead to the M10 is only metre =
long, and shielded, but there are a few inches of unshielded wiring in the =
array.
>
> More intriguingly, the first 20 seconds of the recording don't show the b=
ands. This includes the sounds of me wrapping the array in a towel for wind=
protection. The last part, where I unwrap it again, also doesn't show the =
bands. That I don't understand at all. Unless perhaps my close presence som=
ehow damped some interference?
>
> I've uploaded one minute of it in wav format if anyone wants to have a lo=
ok at it: http://soundcloud.com/petershute/sass-test-harmonics. The first 2=
0 seconds is very noisy and clipped, but I've had to include it to show the=
band free section.
>
> Peter Shute
>
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