Simple Triangular Approximations of Auditory Filter Shapes

Abstract

At present, the most popular auditory filter shape model is one with a rounded peak and exponentially decaying filter skirts (Patterson & Moore, 1986). Unfortunately, the complex nature of this "roex" filter model may, in some instances, have hindered the application of the auditory filter shape in clinical measurements of frequency selectivity. Moreover, some of the assumptions of the roex filter model may be violated at high sound-pressure levels (SPLs) and this limitation has also been a factor when considering the roex auditory filter shape in the clinic. Our purpose is to introduce a simplified method that is adequate for obtaining clinically useful estimates of triangular-shaped auditory filters. Although the triangular-shaped filter model faces the same problems as the roex model at high SPLs, the calculations and assumptions underlying the former are far less complicated. The triangular filter model also retains many of the qualitative properties and advantages afforded by roex-fitted auditory filter shapes. In this report, we review the basic concepts underlying auditory filter shape estimates and describe our methods for measuring and fitting the triangular-shaped filter model. We then present normative triangular filter shapes and compare these estimates with auditory filter shapes fitted by other means. Finally, we present selected examples of triangular filter shapes fitted to the masked thresholds of hearing-impaired patients. For the most part, the triangular-shaped filter model offers the clinician a satisfactory compromise for obtaining estimates of auditory filter shape and frequency selectivity at moderately intense and high SPLs.