Diplacusis associated with bilateral high frequency hearing loss.

Seven normal-hearing subjects and seven subjects with mild bilateral high-frequency sensorineural hearing losses were studied to explore the presence of diplacusis. A tracking procedure of psychophysical method of adjustment-limits was used for pitch judgments rather than the traditional method of adjustment. Each subject was presented with a standard 4000-Hz tone for 500 msec and alternately a variable tone for 500 msec. Subjects were instructed to adjust the variable tone upward or downward in pitch to bracket the pitch sensation of the standard tone. Two intra-aural and two interaural listening conditions were studied. A graphic representation of the subjects' adjustments of the variable tone was obtained for each condition. The resulting tracing indicated frequency correlated to the pitch adjustments from which excursion width and constant error were calculated. Some hard-of-hearing subjects and one normal-hearing subject were found to have diplacusis. Subjects with hearing losses exhibited larger excursion widths for intra- and interaural listening conditions. Subjects with hearing losses tended to be less consistent in pitch judgments than normal-hearing subjects. These findings were interpreted to mean that bilaterally symmetrical hearing losses increase the incidence of pitch aberrations.