Re: [Sursound] KEMAR, Neumann, Zwislocki (Justin Bennett)

[Eric Carmichel]

Greetings,
Some of the first binaural recordings I made were with the Core Sound mics 
attached to my glasses frame (mics very close to conchas, but not in the ears). 
I also made recordings of traffic sounds using the same mics and with a 
KEMAR--the mics, however, were in the KEMAR which then added a resonant peak. A 
nice plus about the Core Sound mics (and this isn't meant to advertise 
anything) is that they fit nicely in KEMAR's 1/4-inch mic clamps (B&K) as well 
as acoustical calibrators designed to accommodate 1/4-inch mics. In fact, I 
continue to use the mics in my own acoustical test fixture that has two ears on 
one side and one ear on opposite side. Impressions of my ears were made to 
create/mold the ears and canal used on the test fixture. The fixture includes a 
strain gauge so that headband force can be measured. Purpose of three-eared 
fixture: To test the efficacy of hearing protection devices to blast noises. I 
can directly compare an occluded and open ear
 with same explosive noise. Anyway... placing the Core Sound (or similar) mics 
on a person gives rise to thoughts of a full-body transfer function and 
unconscious head movements. When listening to recordings made with mics 
attached to my glasses frames, the sense of sounds below is quite remarkable. 
This includes water splashing as vehicles passed by, my own footsteps, and a 
ball bouncing. None if these sounds are as real (place-wise) with recordings 
made via KEMAR or with a second "generic" dummy head. The "full-body" 
recordings may not work for all, and I don't know how they sound when played 
through speakers. But I will certainly state that they are amazingly real 
sounding recordings. Of course, one bias may be that I had a visual of the 
auditory scene, and it was my own minute head movements that may have 
contributed to the place-realism. Always fun to experiment... and learn from 
one's own experiences.
Best,
Eric C.
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Re: [Sursound] Anthropometrics, Loudspeakers, & Vision

[etienne deleflie]

>
> Head width were certainly affect ITDs, but to what extent does this alter
> our sense of sound-source direction? Relatively gross errors seem to have
> minimal affect on lateralization, but this is different from localization
> in 3D. Pinna size and shape alter the spectral nature (name phase /
> amplitude) of higher-frequency, broadband sounds, but we can "re-learn"
> localization ability with a new or different set of ears. Head movement is
> certainly a way of resolving ambiguities


I think head movements do much more than just help in the perception of
discrete spatial attributes, such as sound onset direction. I think they
also contribute by helping our perceptual faculties 'accept' that the
information being presented is correct and reliable. I'm not sure what the
right terminology would be to express this ... maybe one could say that
head movements support the suspension of disbelief, or maybe one could say
that head movements help the perceptual faculties choose the *right*
information to perceive.

One of the characteristics in Gibson's ecological approach that has been
adopted by the VR field is the idea that perceptions are confirmed as true
through 'successful action in the environment'. Tilting one's head can be
considered action in the environment, and if the spatiality of the sounds
heard correlate then that action can be considered successful. So head
movements help to confirm that what is being perceived is correct. Perhaps
a way to describe it is to say that head movements don't just support
quantitative  aspects of perception (eg. "this sound is 45deg +- 5 deg on
the right) but also qualitative aspects: "it sounds real" which leads to
"it must be right".

I read in Handel's text "Listening" (I haven't looked for more substantive
references) that our perceptual systems are more limited by their ability
to *choose* the right information than by their ability to *pick up*
information. I think the tracking of head-movements on headphone listening
systems helps listeners choose the right information, which contributes to
but is significantly different from just helping resolve ambiguities.



> With the eyes closed and subject under constant rotational velocity (i.e.,
> vestibular system in equilibrium or, equivalently, turned off), stationary
> sounds sources appear to move and moving sound sources appear to be
> stationary.


this could be understood in similar terms ... perhaps both the visual field
and the balance system help to confirm that certain information perceived
is the *right* information. I guess one question to ask here is: do the
visual field and vestibular system *add* extra information... or do they
just help the auditory system to choose the right information?

Perhaps one indication would be if the listener's perceptions remain
correct after they have re-closed their eyes. (ie. perhaps the 'learning'
actually exists as 'being able to choose the right info to perceive')

Etienne



> I won't say more at this time because I don't want to pass along info
> without having permission to do so. I'll have a chance to visit Bill's lab
> in the very near future, and ask when the results of the study are slated
> for publication.
>
> Best,
> Eric C.
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