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Introduction

The ear consists of three parts - the outer ear, middle ear and inner ear. Each part of the ear serves a specific role in detecting and interpreting sound. The outer ear collects and directs sound to the middle ear. The middle ear then transforms the energy of a sound wave into the internal vibrations of its bone structure and ultimately into a compressional wave in the inner ear. The inner ear transforms the energy of a compressional wave within the inner ear fluid into nerve impulses which can be transmitted to the brain.





Figure 1: Diagram of the ear

With reference to Figure 1, the middle ear is an air-filled cavity which consists of an eardrum and three minute, interconnected bones - the hammer, anvil, and stirrup. As sound waves vibrate the eardrum, it in turn moves the nearest ossicle, namely the hammer to which it is attached. The hammer then transmits the vibrations, via the anvil, to the stirrup, and ultimately to the opening to the vestibule of the inner ear.

In Australia, 20 children per 10,000 live births will be born with a congenital sensorineural hearing impairment. Sensorineural hearing impairment is caused by damage to, or malfunction of the cochlea or the hearing nerve and hence leads to a loss of loudness as well as a lack of clarity. This can be rectified by the use of middle ear implants. However, candidates for middle ear implants must have a normally functioning middle ear.

The focus of the investigation is the middle ear implant. A modern middle ear implant is a hearing aid of which the receiver or the entire hearing aid is inserted into the middle ear.

Further aspects of this biomedical device such as the materials used to manufacture the device, their biocompatibility, the production process and the relation of the microstructure to function will be discussed at later parts of the report.

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