[net.audio] Equalizers, acoustics, quibbles...

muller@inmet.UUCP (05/11/84)

#N:inmet:2600077:000:2681
inmet!muller    May 10 08:12:00 1984

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A few comments on equalizers, room acoustics, hearing response, etc...
 
If you use an equalizer to correct for your own hearing response curve, it
will sound unnatural, since that curve is what you are use to.  Ideally you
want your stereo to reproduce all frequencies equally, so that the result
will be as close as possible to what it would sound like TO YOU (or anyone
else) if it were real.  Incidentally, we all have a different hearing 
frequency response due to head and ear shape (or hearing damage? (or
musical tastes? (or brain damage??))), etc.  
 
How do you use a record to set up an equalizer?  Your ears should be good
enough for 2dB, but what is your reference other than memory of what good
music "should" sound like?  And HOW do you use it to correct for your own
hearing, without someone else's ears?...There may be a way, but it isn't
obvious.  A pink noise source with calibrated microphone and an analyzer
will do the job, IF it is well made (how do you tell?) and IF the listening
environment is "dead" enough that it isn't influenced greatly by variations
in the furniture, etc, and IF you equalize for the one place you will be
listening from.  If the room is large and "live", you may need to
compensate for the variation of attenuation with frequency.
 
Why "pink" noise?  Isn't "white" noise flat?  Most (all I have ever seen
for ordinary use) analyzers have logarithmic frequency scales, usually 
octave or 1/3 octave.  The value reported for each frequency is really
the integral of the power over that bandwidth.  Since the bands get wider
by a factor of two for each octave (measured linearly), you need noise
which decreases by a factor of 2 (3dB) per octave in order for it to 
"look" flat on the analyzer's display.  Hence, "pink".  If you had linearly
spaced frequency bands, you would want "white" noise. 
 
This may be a minor quibble, but there is a difference between what
electronics does to the music and a SOUND FIELD's behavior.  Room acoustics
may affect how the SOUND behaves, but it doesn't make your STEREO behave
any differently.  An equalizer is an attempt to use the latter to correct
for the former.  Why bring this up?  Well, when we talk about things like
drapes or furniture or other speakers in a room affecting the sound, we
should remember that SOUND is governed by the "laws" of physics and has
been well-understood for a long time.  We should be careful lest we confuse
the TECHNOLOGY of electronics and transducers with the PHYSICS of sound, or
either of these with the PERCEPTION of sound (psychoacoustics).  We can 
improve the first, but we ultimately must react to the second through the
window of the third.