lauck@bergil.DEC (08/08/85)
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When performing double blind tests of audio components one critical factor
is often overlooked: the SAME MUSIC must be played when testing. The
common practice of synchonizing the sources and matching levels is not good
enough to evaluate subtle differences. Consider switching between two notes
of a piece. The two notes may be played on different instruments. The two
notes may be on the same instrument but different pitches. Even when the
pitch is the same the attack, amplitude, etc. may be different. What good
then is all the fancy level matching to .05db?
A while back I compared two CD players with one of these synchronized
listening tests. It was very frustrating. I kept trying to tell whether
the Sony reproduced the violins better than the Nak reproduced the violas.
The result was predictable, no statistical significance. I had previously
compared the players by repeated playing of the same musical selections on
each (not blind, BUT level matched to .05db). In these tests my wife and I
both prefered the Nak. (I guess we're audio snobs.)
A proper scientific test would have involved double blind playing of
identical material. With the equipment and program material available, this
would have meant hours and hours of testing.
Does anyone have any opinions, or better scientific evidence, on the choice
of program material to maximize success (discrimination) of double-blind
testing? For example, I'd like to know what is the optimum length of test
selections. Short selections have the obvious advantage that bigger
statistical samples are practical. Can they be too short to perceive holistic
effects, like the soundstaging of complex orchestral material?
Tony Lauck
...decvax!decwrl!rhea!bergil!lauckrfg@hound.UUCP (R.GRANTGES) (08/10/85)
[] There is something in what you say - about comparing violins on A with violas on B - but not very much. In the first place, if you want to be really rigorous about it and play the same material, many composers have had you in mind when they wrote something called a "repeat"- the same passage repeated. Not all repeats are observed in performance, but enough to satisfy your demand. However, such a test would not be very good because of the incredibly poor audio memory most people have. After a few seconds, you can't reliably remember exactly what something sounded like. So a much better method is to switch rapidly in the middle of a phrase. You are then comparing violins with the same violins, violas with the same violas, etc. and doing so while you can still remember what the previous one sounded like. That is where the necessity for accurate synchronizing comes in. I find I must be real poor because I often have to switch back and forth many times to sense a difference. On the other hand, if you want to disguize a switch, don't do it in the middle of a phrase, do it between phrases because then the listeners <will> be comparing one thing with another and may miss the switch all together. -- "It's the thought, if any, that counts!" Dick Grantges hound!rfg
caf@omen.UUCP (Chuck Forsberg WA7KGX) (08/11/85)
I have found choral music to be the most stringent measure of a speaker's smoothness. If you use some slow moving choral music, the sensitivity to slight mismatches in synchronization between the players should be less than it would be for compositions where the timbre is changing rapidly. -- Chuck Forsberg WA7KGX ...!tektronix!reed!omen!caf CIS:70715,131 Omen Technology Inc 17505-V NW Sauvie Island Road Portland OR 97231 Voice: 503-621-3406 Modem: 503-621-3746 (Hit CR's for speed detect) Home of Professional-YAM, the most powerful COMM program for the IBM PC