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Thread: Headphones changing pitch automagically [OT]
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picon face BY : Brandon, Tom email (remove spam text)



Part of the fatigue of headphones is supposed to be psychoacoustical. The
brain is used to sounds coming from outside of the head from a certain
direction (binaural sound (headphones don't fall under this definition of
binaural sound as there are 2 sources)) while with headphones make the sound
appear to come from inside the head, a quite unnerving experience for the
simplistic (in one way) brain. Tests have shown that people who use auditory
cues (e.g. fighter pilots for radar) get far less fatigue when a binaural
sound is used rather than headphones.

The pitch change may also be psychoacoustical. Frequency spectra are used by
the brain for positioning. It works like this, inside the ear is a thing
called the pinna, when sound enters the ear canal it causes the pinna to
vibrate, the pinna vibration is related to the angle the sound entered the
ear. Thus, the frequency spectrum reaching the eardrum is altered based on
the direction. So if you take headphones off and move them in front of (or
behind) your head but keep them close to your body in the horizontal plane
you will create a very sharp angle to the ear and thus would get larger
modification of the frequency spectra. The pinna is only receptive to sounds
>3500Hz odd so you wouldn't notice the effect with bass, which is why bass
is more omnidirectional. The Aureal 3D system works by applying the HTRF (?
the impulse response of the pinna) to audio. So keep your head REAL straight
when using A3D or your own pinna will effect the calculated final HTRF
percieved by you.

Also, someone brought up bass reponse in in-ear style phones. These
headphones use psychoacpoustical tricks to make your brain hear frequencies
the phones can't produce. It's something like this, if you give the brain 2
sequential (non fundamental) harmonics then it will 'hear' the fundamental
harmonic as well. And if those fundamental harmonics were above 3500Hz (or
one was) then it would only work when the phones were pointed straight into
your ear or the pinna would throw it off.

(NB: All these facts are from memory, read the article last night while half
asleep. I'm quite sure all the ideas are right (as presented in the material
I read) but I apologise if any terms\details are incorrect).

Much of this info came from articles at http://www.headwize.com/ which have
a fair number of articles on the psychoacoustics of headphones\3D sound and
the like.

Tom.

{Original Message removed}
<F08121B734E0D311804300105A7890F771C0@psynt.psy.unsw.EDU.AU>

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Subject (change) Headphones changing pitch automagically [OT]

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