THE CONTOUR TEST OF LOUDNESS PERCEPTION

Objective: This article presents the underlying rationale, normative d ata, and reliability data for a test of loudness perception (the Conto ur Test) that was devised for use in clinical hearing aid fitting. The Contour Test yields data describing the sound level required for each of seven categories of loudness ranging from very soft to uncomfortab ly loud. Design: Two experiments are described. Experiment 1 yielded n orms for the test. The subjects were 23 male and 22 female normal-hear ing listeners. Test stimuli included warble tones at six frequencies a nd broad band speech. Experiment 2 assessed the reliability of the tes t results. Ten hearing-impaired listeners responded to the test at two frequencies on two occasions separated by several days. Both experime nts also evaluated the effect of using different stimulus increment si zes on the measured levels of loudness categories. Results: Based on t he data from experiment 1, norms for each category of each stimulus ar e reported in terms of mean level and typical between-subject variatio n in responses. Data are provided in HA-1 2 cm(3) coupler levels as we ll as in hearing levels (dB HL). The shape of the loudness growth func tion for warble tones was somewhat different from that for speech. Whe n data were expressed in HL, there were no differences in mean loudnes s category levels across warble tone test frequencies. Thus, test freq uencies were combined and equations were generated tea describe the up per and lower limits of typical normal performance for warble tone sti muli. These equations can be used to construct a template for clinical comparison of normative values to patient loudness growth curves. Exp eriment 2 provided information about the test-retest variability of da ta yielded by the Contour Test. Reliability appears to be similar to t hat of the few other category scaling tests described in the literatur e. Most test-retest differences were 6 dB or less. Although a moderate variation in test increment size did not significantly affect the lou dness category levels for young normal-hearing listeners, levels corre sponding to loudness categories ware significantly higher when larger increments were used with elderly hearing-impaired listeners. Conclusi ons: Evidence from this and other research indicates that standardized measurement of loudness perception is an achievable goal for clinical practice. The Contour Test appears to offer a viable approach to clin ical measurement loudness perception: It has good patient acceptance a nd combings fairly rapid administration with acceptable reliability. D etails of test procedures and scoring sheets for manual administration can be da down-loaded from the Internet at www.ausp.memphis.edu/harl. However, it is important to keep in mind that the application of loud ness perception data for narrowband stimuli (such as warble tones) to hearing aid prescription is complicated by the need to account for the effects of loudness summation across bandwidth. There is a need for a dditional research to establish an empirical link between clinically m easured loudness perception and optimal amplification characteristics.