Just audible pitch and loudness modulations with cochlear impairment

Just noticeable combined modulations in amplitude and frequency were determined for an observer (DP) with a bowl-shaped sensorineural hearing loss of about 40 dB between 1 and 2 kHz. In all stimulus conditions, interactions were found between the detection of amplitude modulations and frequency modulations. These interactions appear to correlate quantitatively with the effect of frequency on loudness (as given by the slope of the equal-loudness contour). When this effect of frequency on loudness if taken into account, the data support the hypothesis of independent detection of pitch and loudness modulations. The experimental data are also discussed in relation to the single-mechanism hypothesis for the detection of changes in amplitude and frequency (Zwicker, Maiwald). This model could not provide a satisfactory explanation of interactions between amplitude and frequency.