Message 21921 in TECH.WW
From: G8MNY
Date: Wed, 06 May 26 09:31:00 Z
Newsgroups: TECH.WW
Subject: AF Noise Generator
Message-ID: <59006_GB7CIP>
Path: N2MH4|GB7BED|VE2PKT|VE3KPG|GB7CIP
R:260508/1452Z 30937@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260506/0932Z 10845@GB7BED.#21.GBR.EU LinBPQ6.0.25
R:260506/0931Z 7462@VE2PKT.#TRV.QC.CAN.NOAM LinBPQ6.0.25
R:260506/0931Z 21633@VE3KPG.#ECON.ON.CAN.NOAM BPQ6.0.25
R:260506/0931Z @:GB7CIP.#32.GBR.EURO #:59006 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Nov 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This is a audio noise generator that can make:-
WHITE NOISE that has constant energy per Hz.
PINK NOISE that has constant energy per octave, with a series of CRs to give
a 3dB per octave filtered white noise.
RED NOISE that has reducing noise per octave, with a single CR for 6dB per
octave filtering of the white noise.
SCHEME
PSEUDO RANDOM NOISE GENERATOR
After a count of #34113 the pseudo random noise code repeats.
AF FILTERS
u1 === BUFFER AMP
SPECTRUMS
Level Constant Analyser Bandwidth
0 200 400 600 800 1k 1k2 1k4 1k6 1k8 2k 2k2 2k4 2k6 2k8 3k 3k2 3k4 Hz
Level
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz
Level
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz
With constant Q filters in an AF spectrum analyser display the pink noise
gives a flat response.
Level
16 32 64 125 250 500 1k 2k 4k 8k 16k 32k Hz
With Magnetic systems like tape, magnetic cutting heads, etc. Red noise will
produce a flat spectrum, with constant bandwidth analyser.
SOUND COLOURATION
With good hearing it is possible to judge AF response of system especially
when comparing using just these noises.
The White noise lets you predominately hear the top end, as the ear is like a
constant Q analyser. The Pink noise lets you judge the whole range, while the
Red noise lets you more easily concentrate on the bass resonances.
Used with a good graphic equaliser, mainly of the system colourations
(LS + room etc.) can be mostly ironed out.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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