Objectives: To compare the loudness functions (loudness ratings as a function of sound level) obtained from patients diagnosed as having functional hearing loss (FHL) with those for patients with sensorineural hearing loss (SNHL) and healthy volunteers.
Design: Loudness functions for a 1000 Hz tone for patients with FHL and SNHL were assessed based on the categorical loudness scaling method. The data were compared with control data obtained in our facilities.
Study sample: 18 patients (33 ears) with FHL and 10 patients (19 ears) with SNHL.
Results: For patients with SNHL and healthy volunteers, loudness increased progressively with increasing sound level above the audiometric threshold, with no exceptions. However, for about 70% of the patients with FHL, a different type of loudness function was obtained; the thresholds determined from the loudness function, which were defined as the minimum sound levels at which loudness could be judged, were 10 dB or more lower than the audiometric threshold (>10 dB), and/or the loudness ratings were elevated for a sound at the audiometric threshold.
Conclusions: The results support the hypothesis that patients with FHL often make threshold judgments based on a certain loudness.
Keywords: Békésy audiometry; Functional hearing loss; categorical loudness scaling; loudness function; pseudohypacusis.