Dummyhead Recording / Front-Back shift / FWD from AUDITORY


Subject: Dummyhead Recording / Front-Back shift / FWD from AUDITORY
From: KEVIN AUSTIN (KAUSTIN@vax2.concordia.ca)
Date: Tue Nov 23 1999 - 02:40:44 EST


FYI on binaural recording shifts ... (from AUDITORY)

Sorry for doubles
Best

Kevin
kaustin@vax2.concordia.ca

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  1. front to rear reversals (2)

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Date: Mon, 22 Nov 1999 12:04:29 +0000
From: mup1dm <mup1dm@SURREY.AC.UK>
Subject: Re: front to rear reversals

>Dear List,
>
>I am presently making binaural recordings and attempting to stabilise the
>frontal imaging. Could anyone direct me to resources specifically related
>to solving this problem. Any thoughts on the phenomena?
>
>Tim Cox.

The most obvious reference -- check the bibliography in J. Blauert's
book "Spatial Hearing".

Much of the most recent work will be noted in the book "3-D Sound for
Virtual Reality and Multimedia Applications" by Durand R. Begault.

I have several thoughts on the phenomena, based upon my own
experiences in listening to binaural recordings:

- Different people are different; a recording that works well for
some may not be immersive for others.

- Playing the sum of the two channels from a front centre
loudspeaker can help to generate out-of-head localisation and help
to reduce the front-back reversal effect.

- "head tracking" really helps, if you can make it work in your
situation. Crossfade between recordings made at 5-degree intervals,
or in live situations use a motorised dummy head that moves with the
listener. Most stereophonic systems rely to some extent on our
"willing suspension of disbelief".

In natural listening the soundfield shifts when we move our head. (We hear
a growling lion to our left. As we turn counter-clockwise to face the
lion, the sound of the lion moves clockwise relative to our head.) In
binaural headphone listining the soundfield moves WITH the head. (as we
turn CCW, the sound of the lion moves CCW as well -- remaining FIXED
relative to our head.) This "unnatural" effect may be one cause of the
illusion breaking down.

Douglas McKinnie

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Date: Mon, 22 Nov 1999 08:54:04 -0500
From: John Middlebrooks <jmidd@KHRI1.KHRI.MED.UMICH.EDU>
Subject: Re: front to rear reversals

Tim,

My experience is that there is a lot of variation among individuals
having to do with particular combinations of listeners and sets of
HRTFs. Generally, HRTF properties tend to scale with overall size of
the subject. Small subjects who listen through ears of large subjects
tend to report front/back confusions (particularly down front referred
to down rear), and large subjects who listen through ears of small
subjects report images that are elevated about the actual target. I have
quantified this in a pair of papers in JASA. (Middlebrooks, J. Acoust.
Soc. Am. 106:1480-1492 and 1493-1510, 1999). Good luck.

_________________________________
Dr. John C. Middlebrooks
Kresge Hearing Research Institute
University of Michigan
1301 E. Ann St.
Ann Arbor, MI 48109-0506
voice: 734-763-7965
FAX: 734-764-0014
jmidd@umich.edu

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k



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