ear canal lengths

[Jont Allen <jba@xxxxxxxxxxxxxxxxxx>]

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.

Refs:

 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
> =20
> My question: What RANGE of ear canal lengths are typically observed in
> adults and in children?
> =20
> Thanks in advance...
> =20
> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~=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