Dear Madam or Sir,
I would like to stop becoming email from this list.
Please could you take my email ''measure_0@xxxxxxxxx"
off the list.
> Date: Fri, 14 Nov 2008 11:43:50 +0100
> From: auditorylist@xxxxxxxxxxxx
> Subject: HRTF failure
> To: AUDITORY@xxxxxxxxxxxxxxx
> Dear List,
> We encounter a problem when trying to place a sound at a virtual
> position in space by means of head related transfer functions (HRTF).
> We use sounds from the IAPS database (International Affective Digitized
> Sounds System, Bradley & Lang) as well as simple white noise of six
> seconds duration. We use the Kemar HRTF, the "compact data"
> elevation. We convolve the original sound data with the HRTF data as
> suggested in the documentation. The final sounds are presented using
> Beyer Dynamic DT770 headphones.
> We have tested the precision with which our sounds are placed in virtual
> space, by presenting them to eight listeners. The listeners had a
> touchscreen lying on their lap, with a circle plotted on it, and they
> could indicated the direction where they perceived that the sound came
> from. We presented to them in total 144 sounds, 72 noises and 72 IAPS
> sounds, coming from 36 virtual directions (0°, 10°, 20°...) in
> randomized order.
> The results are shown in a figure that I put in the internet:
> The red dots are from IAPS sounds, the yellow dots are from the noises.
> The x-axis shows the "true" (virtual) angle, the y-axis shows
> estimated angle. As can be seen in this figure, listeners could well
> discriminate between sounds from the left and sounds from the right. But
> not more than that. There is a certain reduction of variance for sounds
> coming from 90° and from 270°, but there is no correlation with angle
> within one hemifield.
> Now we are eager to learn from you: What could be the cause for this
> A) HRTFs are not better than that.
> B) The headphones are inadequate.
> C) It must be a programming error (we don't think so)
> D) ....
> We are grateful for any help in interpreting the possible cause for this
> Thank you very much in advance,
> Christian Kaernbach
> Christian-Albrechts-Universität zu Kiel
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