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From: sjc@angband.UUCP (Steve Correll)
Newsgroups: net.audio
Subject: Re: SR article on CD filtering
Message-ID: <64@angband.UUCP>
Date: Wed, 3-Jul-85 15:32:15 EDT
Article-I.D.: angband.64
Posted: Wed Jul  3 15:32:15 1985
Date-Received: Fri, 5-Jul-85 06:04:14 EDT
References: <386@petrus.UUCP>
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Organization: S-1 Project, LLNL
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> The July issue of Stereo Review has a very good (for an audio magazine)
> article comparing digital and analog filtering techniques...Can anybody
> provide a more complete citation to the JAES article?

Perhaps they are referring to the November 1984 issue, Vol 32 No 11,
"Perception of Phase Distortion in Anti-Alias Filters" by Preis and
Bloom.  The experiment used broadband clicks, not speech or music, and
concluded that the ear is "significantly more sensitive in the middle
of the audio band (4 kHz) than at the upper edge of the band (15 kHz)
to group-delay distortion". Listeners weren't able to discriminate
between unfiltered and filtered sounds with 67% reliability
at 15 kHz until the experimenters cascaded 8 pairs of seventh-order
elliptical anti-aliasing filters. At 4 kHz the listeners scored better
than 67% with only a single pair of elliptical filters. Butterworth
filters made discrimination much harder at 4 kHz, but weren't tried at
15 kHz.

Whether you agree that the experiment proves that such filtering is
inaudible depends, among other factors, on whether you accept the 67%
threshold and whether a test involving clicks is more or less severe than
a test involving speech or music.

-- 
                                                           --Steve Correll
sjc@s1-b.ARPA, ...!decvax!decwrl!mordor!sjc, or ...!ucbvax!dual!mordor!sjc