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Re: Phase Distortion in Headphones

"Frank A. Russo" wrote:
> Dear List,
> I was wondering if anyone had access to or was aware of phase distortion
> characteristics in commercial headphones.  It seems that headphone
> manufacturers are not in the practice of gathering such info or at least
> not in the practice of sharing it with consumers (although they do provide
> harmonic distortion characteristics).
> Alternatively, I would be interested in any suggestion regarding standards
> in assessment of phase distortion.  I'm familiar with the callibration
> technique of comparing a square-wave recorded at output to the original
> pre-processed signal, but I'm not sure about how one would quantify amount
> of phase distortion between the two signals.  Any suggestion would be most
> welcome.
> Thanks!

I would (and have done so in the past actually) measure the group delay.
This does a nice job of characterizing the phase in a meaningful way, and
avoids the problem of flat delay that does not really effect perception.

If the group delay variations, either between the two ears, or across
frequency in one ear, are too large, then you will hear that delay.

There are some good phase perception papers, of maybe 10 or more years ago,
by Doug Pries (if I remember correctly) in the J of the AES.
He is a Prof. at Tufts Univ. I dont think it was earphone listening in his case,
but loudspeaker. Not sure about that.

> -------------------------------------------------------------------------
> Frank A. Russo
> Acoustics Lab, Department of Psychology
> Queen's University, Kingston, ON, K7L 3N6, Canada
> phone:  613-533-2490     fax:  613-533-2499
> russof@psyc.queensu.ca
> http://psyc.queensu.ca/~russof/
> -------------------------------------------------------------------------

Jont B. Allen
AT&T Labs-Research, Shannon Laboratory, E161
180 Park Ave., Florham Park NJ, 07932-0971
973/360-8545voice, x7111fax, http://www.research.att.com/~jba