On Mon, Jun 07, 2010 at 10:34:09AM -0700, Niels Mayer wrote:
> http://nielsmayer.com/db60xg-jaaa-L-noise.png
> shows the noise level at -51db whereas the
> right channel is the more-reasonable -65db
> http://nielsmayer.com/db60xg-jaaa-R-noise.png
Both figures are without any meaning for three reasons:
1. To have a correct idea of what is going on you have to
use a smaller bandwidth (around 1 Hz) will do). As you
decrease the BW, you will see the 'noise level' go down.
showing that this number has no meaning at all.
2. The only valid figure for noise at a particular frequency
is *noise density*, the noise power per Hz. For your
measurement the BW was 16.7 dBHz, so the noise density at
the left (assuming this is noise and not a DC offset or
discrete LF frequencies) is -51 - 16.7 = -67.7 dB/Hz.
You can get this figure without calculation by putting
a noise marker at the required frequency. To get a stable
value use the 'Video Average' function. If the signal
around the marker frequency is truely noise, the noise
density will not depend on BW.
3. Using 'Peak Hold' on noise-like signals produces nonsense.
Ciao,
-- FA O tu, che porte, correndo si ? E guerra e morte ! _______________________________________________ Linux-audio-user mailing list Linux-audio-user@email-addr-hidden http://lists.linuxaudio.org/listinfo/linux-audio-userReceived on Tue Jun 8 00:15:02 2010
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