Newsgroups: sci.electronics
Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!darwin.sura.net!sgiblab!gatekeeper.us.oracle.com!decwrl!gossip.pyramid.com!uunet!world!DPierce
From: DPierce@world.std.com (Richard D Pierce)
Subject: Re: Pink Noise
Message-ID: <C625vv.E96@world.std.com>
Organization: The World Public Access UNIX, Brookline, MA
References: <1993Apr21.231138.20120@uva386.schools.virginia.edu> <34T302tW40N601@JUTS.ccc.amdahl.com>
Distribution: sci.electronics
Date: Sun, 25 Apr 1993 21:19:05 GMT
Lines: 34

In article <34T302tW40N601@JUTS.ccc.amdahl.com> dws30@p1hdb01cd.amdahl.com (David Sharpe) writes:
>
> Pink Noise and White Noise are equal amounts of all frequencies.  This
>is in most cases around the 20-3.3K Hz range.  Pink/White are used to
>adjust for room dynamics and stuff like that.  There are a few EQ's out
>on the market that have Pink noise built in.  Most all from Audio
>Control have them I know the C-101 does.  

Wrong, wrong, completely wrong (and a little misleading, too).

White noise is random noise whose energy density is constant for a
constant bandwidth. That is, a 5 Hz wide band at 20 Hz will have precisely
the same amount of energy as a 5 Hz band at 20 kHz.

Pink noise is random noise whose energy density is constant for a constant
precentage bandwidth. Thus, a 5% wide band of noise at 20 Hz (whose
bandwidth is 1 Hz) will contain the same energy as a 5% wide band at 20
kHz (whose bandwidth is 1000 Hz wide). 

White noise is often used with spectrum analyzers that have constant
bandwidths, pink noise is used with audio-type real-time analyzers whose
bandwidths are centert-frequency dependent (often described as "1/3
octave" or "1/2 octave" or some such terminology).

White noise, relative to pink noise, has more energy at high frequencies
(at a rate equal to 3 dB per octave). Pink noise, relative to white noise,
has more energy at low frequencies (at a rate equl to, again, 3
db/octave).

-- 
|                Dick Pierce                |
|    Loudspeaker and Software Consulting    |
| 17 Sartelle Street   Pepperell, MA  01463 |
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