Randy and/or Sherry wrote:

Patrick Turner wrote:

Would not the use of pink noise through a low pass filter
and used as the carrier signal modulation be a better way to see the
frequency contour on an analyser, why noise + piano?

Absolutely - then you "know" what you're looking at.

Actually the NRSC (I know Patrick -you guys don't have to fool with
such) specifies a white noise source (equal energy at all frequencies)
filtered* then gated at 2.5hz with a 12.5% duty cycle. This is felt to
best simulate "real world" broadcasting. Again see the NRSC-1 spec I
noted yesterday.

I thought white noise had a rising amplitude as F rose.
Pink noise is white noise filtered at a slope of 3 dB/octave,
and thus giving a flat average level amplitude response for any single F
filtered
out of the pink noise, and is thus used for speaker testing etc....

The pink noise gene I made has such a filter applied to a white noise
source.
My bandpass filter for speaker tests has a Q of 12 for any part of the
audio band, and the amplitudes
of the noise bands filterd out from the noise signal is the same between
20 Hz and 20 kHz.

Patrick Turner.



*filter is 100hz high pass 6db/octave and 320hz low pass 6db/octave.
(yes that's -36db @ 10.24khz)

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com