muller@inmet.UUCP (05/11/84)
#N:inmet:2600077:000:2681 inmet!muller May 10 08:12:00 1984 ** ** 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.