Re: spatialisation using headphones ("Ward R. Drennan" )

Subject: Re: spatialisation using headphones
From:    "Ward R. Drennan"  <wdrennan(at)KHRI3.KHRI.MED.UMICH.EDU>
Date:    Fri, 30 Aug 2002 11:40:15 -0400

hamish, Is it a good idea? That I don't know, but if you generate a testable hypothesis, test it avoiding pitfalls and artifacts, and your results add something new to what's known about cross-modal attention, then it's a good idea. A key is developing a knowledge base of what's known and not know about cross-modal attention and addressing a specific, tractable problem. question #2. Using loudspeakers in an anechoic chamber is a good idea, but getting a really good anechoic chamber is difficult. The double-walled booths aren't really anechoic. You could measure reverb times. Also, it might be useful to determine what effect reverb has on bimodal attention. There's so many things that could be studied. Using personalized HRTFs is a second option, but that's time consuming and would require training with people experienced at doing that (see Fred Wightman). There is an AUDIS catalogue of HRTFs which gives I think 10 HRTFs which encompass a variety of headsizes. You can buy it (from France, I think) for a modest fee. I can't seem to find it on the web, but someone on the list may know how to get it. Headphone HRTFs that are not specific to a particular listener tend to give the impression of an image lateralized inside the head rather than an externalized acoustic percept. Such an effect may or may not be good enough for your purposes. It seems that speakers in a room with minimal reverb might be the best/easiest option. Another item of note is this-- pinna spectral cues matter at high frequencies-- i.e. greater than 4KHz and usually in the range of 6- 10KHz, so if you used lower frequency stimuli it's not likely that those cues would be of great concern. Ward Drennan > Hello list! > > I'm a PhD student at the Brain Sciences Institute in Melbourne, about > to embark on my first experiment looking at cross-modal attention > affects on event-related brain potentials. I'm planning on using > simulated "spatial" stimuli in one of my tasks. I have some flashing > lights located on the left, right and center in front of a subject. > There are some beeps that I'd like to play thrpough headphones AS IF > they were coming from the location of the flashing lights. > > They don't have to be exactly localised at the location of the lights, > but I would like them to be vaugely from the same area. What I'm > looking for is a way of "spatialising" my (already made up) sound > stimuli. I'm aware that the HRTF for each person is different, but am > think that perhaps i could use a small set of typical HRTF's that > would cover "large-headed", "small-headed" etc people. > > What I was wondering was > > 1) is this a good idea > 2) where should i start looking for ways of actually implementing > this? > > I have a passing familiarity with MatLab etc > > > many thanks for any pointers in the right direction! > > -hamish- Ward Drennan, Ph. D. Kresge Hearing Research Institute Phone: (734) 763-5159 Fax: (734) 764-0014

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