Click evoked otoacoustic emissions and development of a clinical otoacous tic hearing test instrument

The study of otoacoustic emissions (OAE) from the human ear is introduced with special reference to their clinical applicability. The need for a new instrument is demonstrated, which is capable of measuring click evoked OAEs in the clinical environment. Preparatoiy to the specification and construction of such an instrument, a thorough examination of the transient acoustic response of the ear canal, and the physical properties of the OAE was undertaken. An outcome of this research was the development of a technique which efficiently extracts the cochlear response component from that of the ear canal and middle ear. Various implementations of possible clinical OAE test systems were developed using a minicomputer prototype OAE instrument. A dedicated clinical OAE measurement instrument was designed and constructed to implement the findings of the above. This comprised 2 digital circuit boards and an extensive suite of software based around an IBM PC. Evaluation of the instrument was undertaken during the testing of patients attending the premises for auditory investigations. Operator experience of instrument function are discussed and used for further refinements. The instrument was placed in routine clinical service. Results for patients with a variety of hearing pathologies are discussed. The practical evaluation of the instrument highlighted two areas for further research. Experimental studies were undertaken to establish the role of the middle ear and the value of latency analysis on the OAE. The instrument developed during this project has been introduced into clinical/laboratory service internatio'ially. A discussion of possible further developments of the instrument/technique are given.