Establish the test-retest reliability of loudness scaling using a bounded category rating method.
The individual loudness functions were investigated in three groups of listeners: seven normal-hearing listeners aged 18 to 35 yr, five normal-hearing listeners aged 57 to 84 yr, and five listeners aged 54 to 82 yr with bilateral sloping sensorineural hearing loss. Test-retest reliability was investigated by determining the intralistener, between-session standard deviation.
The pattern of test-retest reliability was similar across all three groups. It improved as the intensity of the stimulus increased: 7 dB at the first quartile of the loudness function, and 3 dB at the third quartile. Two to four runs of the task appear to be sufficient to obtain a stable loudness function, and it was shown that an exponential function provided a better goodness of fit than a linear function (r2: 0.99 compared with 0.94).
Loudness scaling is a longer test than most conventional suprathreshold measures and requires special equipment. However, it has good test-retest reliability and provides more information on the loudness function that might be useful in the fitting of nonlinear hearing aids. The data show that an exponential function provides a good fit to the loudness growth data, and should probably be incorporated into fitting algorithms associated with loudness scaling.
MRC Institute of Hearing Research, Royal Infirmary, Glasgow G31 2ER, Scotland
Address for correspondence: Ken Robinson, Ph.D., MRC Institute of Hearing Research, Royal Infirmary, Glasgow G31 2ER, Scotland.
Received August 7, 1995; accepted November 2, 1995