Models of the auditory threshold

The theory of signal detectability is introduced and audiological methods derived from the theory are discussed. In particular the two inter':al forced choice (2.I.F.C.) procedure in conjunction with an automatic threshold seeking method is selected for detailed study. Sequential strategies and decision rules for the location of specific points on a psychometric function are introduced as the basis of the automatic threshold seeking method. To aid in the study of the resultant 2.I.F.C. automatic threshold seeking procedure the advantages of computer models of the human auditory system at threshold are considered. Details of models, based on the properties of pseudo random binary sequences (p.r.b.s.), are then presented. The models consist of an hardware electronic simulation of the auditory threshold and a digital computer program simulation or software model of the hardware system. Tests to confirm the feasibility of the models are undertaken. A software simulation of the complete 2.I.F.C. automatic threshold seeking system, incorporating the threshold model, is then examined, and the properties of the system discussed. Design considerations of a 2.I.F.C. automatic threshold seeking experimental facility are then outlined. This is followed by the description of an experiment incorporating the hardware threshold model to assess the feasibility of the experimental facility. Details of subjective tests with the experimental facility are then presented. Statistical comparisons of subjective and model dorived data are undertaken to confirm, within the limitations discussed, the validity of the auditory threshold models. The concluding chapter examines the use of an on line general purpose digital computor in this area of research and explores an alternative method of study for future research