On 04/01/2012 11:55 AM, Augustine Leudar wrote:
I am getting a many opinions on this as possible and I have now heard
various answers. It specifically relates to boosted band and, in this
scenario, elevation cues in the median plane . Blauert's 1969 experiment
showed that if an if a narrow band noise or sinusoid wave with a centre
frequency of 8 khz is played to both ears equally the sound is generally
localized above the head. My question is how does the auditory system
distinguish between 8khz as a directional elevation cue or a boosted 8 khz
that might be present in a soundsource directly in front of the listener ?
So far I have been told its to do with binaular differences between the two
ears (the directional bands may not be the same in each ear due to the
different shapes of the pinna and can be compared, visual cues, envelope
shapes) any clarification or alternatives would be great.
off the top of my head, i think blauerts findings were as follows:
* narrow-band artificial test signals fed to both ears in the same way
produce unambiguous auditory events located at various elevations on the
median plane, the elevation depending only on the center frequency.
this phenomenon is more or less the same with different individuals.
* the brain can use elevation-dependent linear distortion of
sufficiently wide-band signals to infer height, but this only works with
familiar signals where an un-elevated (and hence uncolored) reference is
known to the subject.
e.g. some synth signal: practically no height cues
a human voice: usable height cues
your spouse or close friend: quite good height cues
so you can exploit this by boosting any given sound in blauert's
critical bands to give some height impression, but don't expect miracles.
even with proper soundfield reconstruction, the human ability to judge
height is not too good, unless the listener tilts her/his head. visuals
or content usually win over actual direction, i.e. a sound is where you
think you see its source, and birds are up, footsteps are down.
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