well, I think it's a big jump, so to speak to try to get funding for that.
I have a much more modest proposal:
Is auditory spatial perception and performance similar in all regions? - I have
a strong suspicion that it's different in the Maldives. Further, I think it may
be that, if you take someone that has been tested in, say, England, then
transport them to the Maldives and test, looking for changes in performance
over a 2 month period, one might find a progressive change. Then bring them
back for a two month, repeating the test procedure. Then back to the Maldives,
testing if the change in performance is similar, or indeed more rapid, the
second time around.
If significant results are obtained, we next try Bali. and so on.
This will be much cheaper than the zero-G proposal
In the interests of science, I am prepared to volunteer as a guinea pig, even
if it means turning my back on my chances of being promoted to fourth assistant
to the deputy office manager - that's how dedicated to science I am!
Dr Peter Lennox
School of Technology,
Faculty of Arts, Design and Technology
University of Derby, UK
e: p.len...@derby.ac.uk
t: 01332 593155
________________________________________
From: sursound-boun...@music.vt.edu [sursound-boun...@music.vt.edu] On Behalf
Of Dave Malham [dave.mal...@york.ac.uk]
Sent: 05 November 2012 16:28
To: Surround Sound discussion group
Subject: Re: [Sursound] Vestibular response, HRTF database, and now with
added height...
Hi Peter,
Like I just said - needs experiments in zero G. I wonder what the
acoustics in the ISS are like? Might be easier to organise decent
acoustics in a Vomit Comet
(http://en.wikipedia.org/wiki/Reduced_gravity_aircraft) especially as
the padding already there would help. Now, where do we apply for
funding??
Dave
On 5 November 2012 14:18, Peter Lennox <p.len...@derby.ac.uk> wrote:
> Eric, some interesting thoughts there, thanks.
> One or two thoughts in reaction:
> 1) you say " There have been a lot of studies regarding localization in the
> transverse (horizontal) plane" - I know its quite common to conflate these,
> but (as implied in your later thought experiment) - it's worth pointing out
> that "horizontal" is specified as perpendicular to gravity. When a person is
> standing or sitting straight, then if the head is not tilted then the
> conflation is permissible. But. People tilt and move their heads all the
> time, so acuity in hearing in the transverse plane is not the same as acuity
> in the horizontal plane
>
> 2) Your question about acuity when the body is not in that 'usual'
> orientation: I've thought the same thing, though the other way around - I put
> people flat on their backs, then played ambisonic material tilted through 90
> degrees, to see if they got some different experience. So, I was interested
> in perception in the vertical, but using that transverse plane. The
> experience was different, but inconclusive in that it wasn't a controlled
> experiment, of course. I found that identification of source direction was
> less good than I'd anticipated. BUT - actually, (going back to experiences
> whilst camping - I've lain awake in the countryside thinking about these
> things) - listening (especially for direction) with your head so close to the
> ground is certainly an unfamiliar experience. You've messed up a lot of the
> pinnae effects. Interaural differences may well be affected. You've got a
> peculiar pattern of very early reflections (from the ground next to your
> ears). Most importantly,
y
> ou're listening to sources in the sky, with no reflective and occlusive
> bodies around them. There's no 'ground effect' of the sort that a standing or
> sitting person will get - that it, early reflected material that has
> interacted with the ground, including filtering by surface features, clutter
> (material objects and detritus have a tendency to be near the ground due to
> gravity...) so, overall, hearing in that area just won't be the same.
> The above might partly account for why, in your experiment, hearing in the
> horizontal might seem better than it ought - there are simply more cues
> available for sources at or near the ground? However, in the camping example,
> I did find increased instances of reversals.
>
> So I had thought there might be an interaction between gravity and spatial
> hearing, but realised that some of it is just down to physics - the sky
> really is different from the ground, we really are sort of "2.5 d" hearers
> (and thinkers?). I'd also wondered whether distance(range) perception might
> differ with direction. It does (items seem nearer), but more to do with the
> physics of the matter - for sources in the sky, sometimes (not always!) there
> is only a direct signal path. So, distance perception as the product of the
> direct/indirect ratio doesn't seem quite the right formulation.
>
> These things need some decent experimentation, it seems to me
>
> Cheers
> ppl
>
>
> Dr. Peter Lennox
>
> School of Technology,
> Faculty of Arts, Design and Technology
> University of Derby, UK
> e: p.len...@derby.ac.uk
> t: 01332 593155
>
> -----Original Message-----
> From: sursound-boun...@music.vt.edu [mailto:sursound-boun...@music.vt.edu] On
> Behalf Of Eric Carmichel
> Sent: 03 November 2012 18:54
> To: sursound@music.vt.edu
> Subject: [Sursound] Vestibular response, HRTF database, and more
>
> Greetings,
> Mostly through serendipity, I have had the pleasure and privilege of great
> teachers. I studied recording arts under Andy Seagle (andyseagle.com) who
> recorded Paul McCartney, Hall & Oats, and numerous others. My doc committee
> included Bill Yost, who is widely known among the spatial hearing folks. And,
> of course, I've learned a lot about Ambisonics from people on this list as
> well as a plethora of technical articles.
>
> I recently sent an email to Bill with the following question/scenario. I
> thought others might wish to give this thought, too, as it gets into HRTFs.
>
> There have been a lot of studies regarding localization in the transverse
> (horizontal) plane. We also know from experiments how well (or poorly) we can
> localize sound in the frontal and sagittal planes. By simply tilting someone
> back 90 degrees, his/her ears shift to another plane. This is different from
> shifting the loudspeaker arrangement to another plane because the
> semicircular canals are now in a different orientation. If a circular speaker
> array was setup in the coronal plane and the person was lying down, then
> his/her ears would be oriented in such a way that the speakers now circle the
> head in the same fashion as they would in the horizontal plane when the
> person is seated or standing. It's a "static" vestibular change, and gravity
> acting on the semicircular canals (and body) lets us know which way is up.
> But do we have the same ability to localize when the body is positioned in
> different orientations, even when the sources "follow" the orientation (as
> is the case
in
> the above example)? How about localization in low-g environments (e.g.
> space docking)? The question came to me while camping. I seem able to
> pinpoint sounds quite well in the (normal) horizontal plane despite a skewed
> HRTF while lying down (and somewhat above ground).
>
> On another (but related) topic, I have downloaded the HRTF data from the
> Listen Project, and have been sorting the participant's morphological
> features. I have this in an Excel spreadsheet, and am converting this to an
> Access database. Using the data, one can pick an "appropriate" HRTF starting
> with gross anatomical features (such as headsize) and whittle it down to
> minute features (such as concha depth or angle). I find HRTF discussions
> interesting, but still argue that headphones and whole-body transfer
> functions make a difference, too. Insert phones destroy canal resonance,
> whereas an earcup with active drivers may have a large "equivalent" volume,
> thus minimizing external meatus/earcup interaction (a mix and match of
> resonances). Because of this, there can be no ideal HRTF, even when it
> matches the listener.
>
> While listening to HRTF demos, the notion of auditory streaming and auditory
> scenes came to mind. Some sounds were externalized, but other sounds of
> varying frequencies, while emanating from the same sound source, appeared in
> my head. The end result was that the externalized sounds provided a
> convincing (or at least fun) illusion, but problems do persist. A stringent
> evaluation of HRTF / binaural listening via headphones would require breaking
> the sounds into bands and seeing if a sound's constituent components remain
> outside of the head. When doing so, a brick-wall filter wouldn't be
> necessary, but a filter that maintains phase coherency would be recommended.
> The demo I refer to was that of a helicopter flying overhead. Though I
> haven't done this (yet), it would be interesting to use FFT filtering to
> isolate the turbine whine (a high-pitched sound) from the chopper's blades.
> The high-pitched sound appeared to be in my head, whereas the helicopter as a
> whole seemed externa
li
> zed. Again, an individualized HRTF and different phones may yield different
> results. Side note: Be careful using FFT filtering--it can yield some
> peculiar artifacts.
>
> I am hoping to use headtracking in conjunction with VVMic to model different
> hearing aid and cochlear implant mics in space. This offers the advantage of
> presenting real-world listening environments via live recordings to
> study/demonstrate differences in mic polar patterns (at least first-order
> patterns) and processing without the need for a surround loudspeaker system.
> In fact, it's ideal for CI simulations because an actual CI user never gets a
> pressure at the eardrum that then travels along the basilar membrane,
> ultimately converted to nerve impulses. With VVMic and HRTF data, I should be
> able to provide simulations of mics located on a listener's head and then
> direct the output to one or both ears. This does not represent spatial
> listening, but it does represent electric (CI) hearing in space. Putting a
> normal-hearing listener in a surround sound environment with mock processors
> and real mics doesn't work because you can't isolate the outside (surround)
> sound from the i
nt
> ended simulation, even with EAR foam plugs and audiometric insert phones.
> VVMic and live recordings via Ambisonics is a solution to creating "electric"
> listening in the real world. Again, I'm referring solely to CI simulations.
> With the advent of electric-acoustic stimulation (EAS), more than one mic is
> used per ear: One for the CI and a second for the HA. Combinations of polar
> patterns can be created. Respective frequency responses and processing can be
> sent to one or two ears (diotic and dichotic situations). One caveat for
> using vocoding to mimic CIs is that the acoustic simulation (and therefore
> stimulation) still necessitates a traveling wave along the normal-hearing
> listener's basilar membrane. The time it takes to establish a wave peak is
> not instantaneous (though compressional waves in the the inner ear are
> virtually instantaneous), and I believe a time-domain component to inner ear
> (mechanical) action can't easily be excluded when using "acoustic" simulation
> of CIs. I suppose I could look at data from BAERs and the Greenwood
> approximatio
n
> to account for the time-frequency interaction. Just some thinking... and
> ideas to share with others interested in hearing impairments.
>
>
> By the way, Teemko, if you're reading this, just wanted to let you know that
> Bill Yost said he'd read your thesis over the weekend. I notice that Bill and
> Larry Revit are in your references list. Larry isn't a fan of
> Ambisonics--said to me in a phone communication that it sounds "tinny". I
> suppose it does if one were to listen through laptop speakers or from poor
> source material. Not sure what his source was.
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--
As of 1st October 2012, I have retired from the University, so this
disclaimer is redundant....
These are my own views and may or may not be shared by my employer
Dave Malham
Ex-Music Research Centre
Department of Music
The University of York
Heslington
York YO10 5DD
UK
'Ambisonics - Component Imaging for Audio'
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