Re: AUDITORY Digest - 22 May 2002 to 23 May 2002 (#2002-83)

[Jont Allen <jba@xxxxxxxxxxxxxxxxxx>]

Automatic digest processor wrote:

> There are 2 messages totalling 106 lines in this issue.
>
> Topics of the day:
>
>  1. Transfer function of middle ear
>  2. Middle ear transfer function
>
> ----------------------------------------------------------------------
>
> Date:    Thu, 23 May 2002 07:51:18 -0400
> From:    Jont Allen <jba@AUDITORYMODELS.ORG>
> Subject: Transfer function of middle ear
>
> Vivek,
> The middle ear acts as a high pass filter, with a cutoff about 800 Hz.
> It is almost
> flat from 800 to 20 kHz or so, depending on the size of the middle ear
> (i.e.,
> the head). There is a very large literature, much of it in the Jol. of
> the Acoustical
> Soc. of America. Look at the following papers, for example:
>
> @article{Guinan67,
> author={Guinan, J. J. and Peake, W. T.},
> year={1967},
> title={Middle-ear characteristics of anethetized cats},
> journal=JASA,
> volume= {41},
> pages={1237-1261}
>        }
>
> @inproceedings{Shaw78,
> author={Shaw, Edgar A. G.},
> year={1978},
> booktitle={Acoustical Factors Affecting Hearing Aid Performance},
> title={The acoustics of the external ear},
> editor={Studebaker, G. A. and Hochberg, I.},
> publisher={University Park Press},
> address={Baltimore, MD},
> pages={109--125}
>        }
>
> @article{Stinson82,
> author={Stinson, M., Shaw, E.A.G. and Lawton, B.W.},
> year={1982},
> title={Estimation of acoustical energy reflectance at the eardrkum from meas
> urements of pressure distribution in the human ear canal},
> journal=JASA,
> volume={72},
> pages={ 766-773}
>        }
>
> @article{Puria91b,
> author={Puria, Sunil and Allen, Jont B.},
> year={1991},
> title={A parametric study of cochlear input impedance},
> journal=JASA,
> volume={89},
> number={1},
> month=jan,
> pages={287-309}
>        }
>
>
> --
> Jont B. Allen,     jba@auditorymodels.org;   908/654-1274voice; 908/789-9575 fax
> 382 Forest Hill Way
> Mountainside NJ 07092
> http://auditorymodels.org/jba
>
>
> ``It is hard to abandon the feeling that the unfamiliar is absurd and illogical.''
>        --G.A. Miller, p. 5 of his book `Language and communication'
>
> ------------------------------
>
> Date:    Thu, 23 May 2002 15:50:49 +0100
> From:    "Brian C. J. Moore" <bcjm@CUS.CAM.AC.UK>
> Subject: Middle ear transfer function
>
> Dear List,
>
> While I always hesitate to disagree with Jont Allen, my interpretation of
> the literature is that the middle ear transfer function, measured as the
> ratio of cochlear pressure to pressure at the ear drum, is not flat from
> 800 Hz to about 20 kHz, but is more like a bandpass function, rolling off,
> in humans, above 5 kHz.
I do agree with Brian, that there is some roll-off above a few kHz.
There is a great deal
of variability between ears on this point. It is my interpretation of
the data,
That really high quality ears (having no dammage) show less of this rolloff
between 5 and 20 kHz. But there is no doubt that it is there in the majority
if not all ears, to different degrees.  I am guided by Fig. 10 of
Puria and Allen, JASA, Vol. 104(6), Dec. 1998 page 3474.
I have placed a .jpg file of this figure at the following URL:

http://auditorymodels.org/jba/images/MEFig10.jpg

This figure shows a 10 or so dB attenuation between 5 and 20 kHz.
That is 10 dB in 2 octaves, or 5dB/oct.
Remember, speech contains information from 300 Hz to 7 or 8 kHz.
So this effect is quite small on the speech signal.

Jont

> See:
>
> Puria, S., Rosowski, J. J. and Peake, W. T. (1997). Sound-pressure
> measurements in the cochlear vestibule of human-cadaver ears, J. Acoust.
> Soc. Am. 101, 2754-2770.
>
> Aibara, R., Welsh, J. T., Puria, S. and Goode, R. L. (2001). Human
> middle-ear sound transfer function and cochlear input impedance, Hear. Res.
> 152, 100-109.
>
>
> Brian C. J. Moore, Ph.D., FMedSci, FRS
> Professor of Auditory Perception,
> Department of Experimental Psychology,
> University of Cambridge,
> Downing Street,
> Cambridge CB2 3EB,
> England
> Tel. + 44 1223 333574
> Fax. + 44 1223 333564
> http://hearing.psychol.cam.ac.uk/
>
> ------------------------------
>
> End of AUDITORY Digest - 22 May 2002 to 23 May 2002 (#2002-83)
> **************************************************************
--
Jont B. Allen,     jba@auditorymodels.org;   908/654-1274voice; 908/789-9575 fax
382 Forest Hill Way
Mountainside NJ 07092
http://auditorymodels.org/jba


``It is hard to abandon the feeling that the unfamiliar is absurd and illogical.''
       --G.A. Miller, p. 5 of his book `Language and communication'