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From: levy@ttrdc.UUCP (Daniel R. Levy)
Newsgroups: net.audio,net.auto
Subject: Re: Phase distortion on music
Message-ID: <769@ttrdc.UUCP>
Date: Sun, 2-Mar-86 16:41:07 EST
Article-I.D.: ttrdc.769
Posted: Sun Mar  2 16:41:07 1986
Date-Received: Fri, 7-Mar-86 06:30:54 EST
References: <1582@emory.UUCP> <523@eneevax.UUCP> <445@unccvax.unccvax.UUCP> <1211@mtx5a.UUCP> <12077@ucbvax.BERKELEY.EDU>
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<Oh oh here it comes.  Watch out boy, it'll chew you up! \
Oh oh here it comes.  The LINE EATER!  [Line eater]>

In article <12077@ucbvax.BERKELEY.EDU>, spp@ucbvax.BERKELEY.EDU (Stephen P Pope) writes:
>I don't remember the reference, but one psychoacoustic study
>showed that, for speaker crossovers, the phase distorion was
>found to be inaudible (under the condtions of this study)
>so long as the frequency response is smooth in the region where
>the phase change vs. frequncy was high.  If the frequency
>response was uneven, the phase shift was very noticible.
>Hence the conclusion, human hearing is insensitive to phase
>shift if the frequncy response is flat.  However, this obviously
>can't be generalized to the multiple radians of phase shift
>found in the passband of a sharp-cutoff LPF, as the CD makers
>have found out.
>There's also the irrelevant fact that phase carries no information
>in speech.
>steve

Way back when I was in undergrad EE, I learned that the effect of making
a phase shift in one component of some waveforms could, if the shift was
correct, cause the waveform to have extremely sharp (theoretically tend-
ing to infinity) peaks.  This would pose an obvious problem for the faith-
ful reproduction of those waveforms, even setting aside the issue of whether
it "sounds the same."  (Which I doubt it would, since it would push the
ear itself to mechanical extremes during the peaks.)  Note I am not saying
that the TOTAL ENERGY of the peaks tended to infinity (obviously impossible
when starting out with a signal of finite power) but just that the INSTANT-
ANEOUS (current, voltage, power) level did.
-- 
 -------------------------------    Disclaimer:  The views contained herein are
|       dan levy | yvel nad      |  my own and are not at all those of my em-
|         an engihacker @        |  ployer or the administrator of any computer
| at&t computer systems division |  upon which I may hack.
|        skokie, illinois        |
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