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Re: Lateral Inversion in Spatial Hearing

"Houtsma, A.J.M." wrote:
> -----Original Message-----
> From: Heinrich Zimmermann [mailto:hzimmer@IAM.UNIBE.CH]
> Sent: zaterdag 25 september 1999 11:39
> Subject: Re: Lateral Inversion in Spatial Hearing
> First Summary: Lateral Inversion in Spatial Hearing
> On September, 2nd, I have put the following query on this list:
> > I wonder if anybody on the Auditory List knows something about a lateral
> > inversion phenomenon I discovered when preparing sounds for a series of
> > experiments on spatial hearing: certain binaural recordings of
> > bandpass-filtered clicks with interaural time differences but without
> > interaural intensity differences seem to be lateralized as predicted by
> > cross-correlation models in a frequency range below 2 Kilohertz but on the
> > opposite side than predicted by these models in a frequency range above
> > 8 Kilohertz.
> In response to some of your questions I have put an example sound file for
> the lateral inversion phenomenon on http://Heinrich.Zimmermann.com
> <http://Heinrich.Zimmermann.com> .
> ------------------------------------------------------------------------
> Dear Heinrich,
> I listened to your sound sample and, indeed, the chirp apears to come from
> the right. Analysis
> of the sound, however, shows several confounding artifacts.
> (1) There is an annoying ringing in the 'silent' portion of the signal
> before and after the click,
>      particularly in the right channel. It is a mix of a 2-kHz and 8-kHz
> tone, corresponding to
>      the edges of your extremely steep bandpass filter. This tone sets a
> strong bias towards
>      the right ear and could explain the whole 'lateral inversion'
> phenomenon.
> (2) The right signal is not only 500 microsec. delayed, but also phase
> distorted. Did you use
>      separate independent filters?. This phase distortion causes the image
> to diffuse.
> (3) Measured over the signal (click-response) portion, there is an intensity
> difference of about
>      0.5 dB between the signals, the left signal being the more intense.
> I therefore generated a somewhat cleaner signal this morning, starting with
> an analog
> 10-microsec. pulse bandpass filtered between 2000 and 8000 Hz by two Kemo
> filters
> in series (about 190 dB/oct). This signal was put in the left channel of a
> stereo wav file.
> In the right channel was either exactly the same signal (click.wav) or that
> same signal
> delayed by 500 microsec. (clickster.wav). Each file contains 5 clicks, 1
> sec. apart. If
> you play them in this order, you will quite convincingly hear the first five
> clicks in the
> center and the next five clicks to the left of the center. Just as the
> textbooks tell you.
> I have attached both files as wav attachments. Enjoy the clicks.
> Adrian Houtsma
>   ------------------------------------------------------------------------
>                 Name: click.wav
>    click.wav    Type: WAV Audio (audio/x-wav)
>             Encoding: base64
>                     Name: clickster.wav
>    clickster.wav    Type: WAV Audio (audio/x-wav)
>                 Encoding: base64