external ears' influence on hearing

Jeffrey Sirianni sirianni at uts.cc.utexas.edu
Fri Mar 10 00:25:34 EST 1995


In article <3jnlcb$4ua at calvin.usc.edu>, phelps at calvin.usc.edu (Charles V. Phelps) says:

{SNIP}

>If I push my ears forward, or cup my hands around my ears, I notice
>a big difference in my hearing acuity.

{SNIP}

>Wouldn't this variation play a large role in how well someone hears? I
>would think that it would also play a role in how well one could
>distinguish a significant sound (like someone talking) from background
>noise.

It true that the loudness of a sound that we are trying to hear increases
when we poition our pinna to "capture" more of the sound heading toward
our ears.  I think we get about a 3 dB increase in loudness.  It sure helps
us when we are trying to hear a soft sound coming from across the room.
As for listening in noise, I guess the only way that is can help is if the
source of the sound we are trying to listen to is in from of us and we position
out pinna so that it is perpendicular to the incoming sound waves.

>The ear size/shape factor would not be picked up in tests that
>use earphones.

True....

>I can see why such tests are done, but is
>there any reason they are not supplemented with other tests, where
>the source of the sound is some distance away, to see how well the
>subject hears in a "real-world" situation?

Audiometric testing has been "standardized" so that pinna shape does
not effect the results of the test.  I know that this is not "real world"
data, but we use it as a standard across all people.

If you are interested in pinna effects, there is a classic 1972 (?) article
by Shaw, where each of the outer ear componets were analyzed in their relative
contribution to hearing and localizing.  If someone knows the reference off-hand,
I'm sure it would be appreciated.


>Charles Phelps
>Science & Engineering Library
>University of Southern California
>phelps at calvin.usc.edu

Jeff Sirianni     @(((<{
University of Texas at Austin
Communication Sciences and Disorders
CMA, 2nd Floor Clinic
Austin, TX  78712-1089
sirianni at uts.cc.utexas.edu
jgsaudio at aol.com



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