Australian Acoustical Society ABN 28 000 712 658 A.C.N. 000 712 658

ARTICLES

The Ear as an Acoustical Transducer
G K Yates

Hair Cells - Mechanosensors and Motors
J O Pickles

The Ear as an Acoustical Generator: Otoacoustic emissions and their diagnostic potential
E L Le Page, N M Murray, K Tran, M J Harrap

The University of Melbourne/Nucleus Multiple-Channel Cochlear Implant
G M Clark

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The Ear as an Acoustical Transducer

Graeme K. Yates
The Auditory Laboratory
Department of Physiology
The University of Western Australia
Nedlands, 6009

Vol. 21 No. 3 pp 77 - 81 (1993)
ABSTRACT: Biology has imposed several severe limitations on the ear in evolving as the biological equivalent of a microphone. Speed of response, dynamic range and sensitivity are all limited by the raw materials of the nervous system. In adapting to overcome these limitations, the ear has developed some unique solutions that enable it to perform as well or better than many commercially available microphones.

Hair Cells Mechanosensors And Motors

James O. Pickles,
Vision Touch and Hearing Research Centre,
Department of Physiology and Pharmacology,
University of Queensland,
Brisbane, 4072

Vol. 21 No. 3 pp 82 - 85 (1993)
ABSTRACT: Hair cells are the mechanosensors in the cochlea. They detect acoustic vibrations as a result of deflection of the hairs, or stereocilia, on their surface. In addition, hair cells are bidirectional transducers, and return energy to the mechanical system. The bidirectional transduction is responsible for the high sensitivity, high degree of frequency selectivity, and extended frequency range typical of mammalian hearing.

The Ear as an Acoustical Generator: Otoacoustic emissions and their diagnostic potential

E.L. LePage¹, N.M. Murray¹, K. Tran¹, and M.J. Harrap²¹Hearing Conservation Research Unit
National Acoustic Laboratories
126 Greville Street,
Chatswood, N.S.W. 2067.

²Acoustics and Vibration Centre
University College
Australian Defence Force Academy
Canberra, ACT 2600

Vol. 21 No. 3 pp 86 - 90 (1993)
ABSTRACT: When sound enters the cochlea it evokes an electromotile response of the outer hair cells which is present in normal ears but absent in mild sensorineural hearing loss. This activity modifies the mechanical motion of the basilar membrane nonlinearly if the stimulus frequency is close to the characteristic frequency of each place. A bi-product of this motor activity is a reverse travelling wave which may be detected as a sound in the ear canal with a sensitive microphone. Such sounds may be spontaneous or may be evoked by specific test stimuli such as clicks or pure tones. Analysis of these emissions provides a map of damage to the ear which apparently may be extensive before any sign of hearing loss occurs. The difference between estimated age and chronological age for any ear may provide early warning of increased susceptibility to hearing loss which may be useful in the prevention of hearing loss. Time-frequency distributions may offer an approach to the dynamic characterisation of specific outer hair cell pathologies to assist in the determination of susceptibility.

The University of Melbourne/Nucleus Multiple-Channel Cochlear Implant

Graeme M. Clark
Department of Otolaryngology,
The University of Melbourne, and
The Australian Bionic Ear & Hearing Research Institute,
East Melbourne

Vol. 21 No. 3 pp 91 - 52 (1993)
ABSTRACT: The histoiy of the development of the multiple-channel cochlear implant by a research team at the University of Melbourne, in collaboration with Nucleus Ltd, is reviewed and related to various strategies for speech processing and cochlear stimulation for the profoundly deaf. The results of clinical trials are summarised and evaluated.