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ear canal lengths

Hi Sarah,

I suggest you tread lightly on this topic with your students. The ear
canal is terminated in an impedance that is close to the characteristic
impedance of the canal (i.e., rho*c/area). Thus the classical idea of a
resonance is really a false concept here. For example, if one were to
look at the reflectance in the canal, it depends on frequency. The idea
of a canal resonance seems to be based on a false assumption that says
the ear drum is rigid. There is a passive gain (12 dB@ 2.5kHz, Shaw JASA
1974) associated with the pinna, canal and drum, but I am suggesting
that the simple idea of a canal resonance is a false analogy.

What do others think? Comments Welcome.


 author = {Puria, S. and Allen, J. B.},
   title = {A parametric study of cochlear input impedance},
   journal = JASA,
   volume = {1},
   number = {89},
   pages = {287-309},
   month = jan,
   year = {1991}

author = {Voss, S. E. and Allen, J. B.},
   title = {Measurement of acoustic impedance and
        reflectance in the human ear canal},
   journal = JASA,
   volume = {95},
   number = {1},
   pages = {372-384},
   month = jan,
   year = {1994}

Jont Allen

Hello all - I'm teaching my Physics of Speech students about ear canal
resonances today and want to create examples and homework problems that
include actual ear canal lengths, but am having trouble finding this
information on the web.=20
My question: What RANGE of ear canal lengths are typically observed in
adults and in children?
Thanks in advance...
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~=20
Sarah Hargus Ferguson, Ph.D., CCC-A
Assistant Professor
Department of Speech-Language-Hearing: Sciences and Disorders
University of Kansas
Dole Center
1000 Sunnyside Ave., Room 3001
Lawrence, KS  66045
office: (785)864-1116
Speech Acoustics and Perception Lab: (785)864-0610