Re: HRTF failure ("Richard F. Lyon" )

Subject: Re: HRTF failure
From:    "Richard F. Lyon"  <DickLyon@xxxxxxxx>
Date:    Fri, 14 Nov 2008 07:38:05 -0800

Christian, If you interpret the pattern in your GIF plot as a pair of big "X" patterns, you can see it represents primarily a front-back confusion. This is very typical with headphone listening. There is lots of literature on this particular difficulty and ways to improve it: Dick At 11:43 AM +0100 11/14/08, Christian Kaernbach wrote: >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" with zero 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 the >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 failure? > >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 failure. > >Thank you very much in advance, >Chris > >-- >Christian Kaernbach >Christian-Albrechts-Universität zu Kiel >Germany >

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