Design optimization and evaluation of integrating sound level meters.

Previous work has shown that the risk of hearing loss is related to the cumulative sound energy received by the ear. The instrument which computes a measure of this parameter is an integrating sound level meter (ISLM). Optimum design requirements for ISLMs which meet a variety of demanding specifications have been determined. Evaluation procedures have been proposed and the necessary specialized tone burst signal sources have been designed. An early survey of instruments which were available revealed serious shortcomings in their ability tointegrate accurately a typical impulsive signal. The aim of this work was to determine and critically evaluate the limiting mechanism, and to subsequently investigate design strategies leading to high performance instruments. Techniques for extending the performance of several standard circuits have been developed. In addition, a novel method for storing data in analogue and digital form and subsequently recovering a continuous output has been developed and is fully described. Combinations of analogue, random logic and microprocessor-based techniques have been investigated. Complete instruments which utilize different combinations have been designed and evaluated. The optimum performance for an instrument which meets the highest specification is shown to be achieved by the use of analogue techniques for the majority of the signal processing, with a combination of random logic and microprocessor-based techniques for control and data storage.