Category loudness scaling to evaluate sound perception in cochlear and retro-cochlear lesions

Category loudness scaling was used to investigate the loudness perception o f 31 patients with a cochlear hearing loss (Group 1) by comparing the resul ts with those found in 15 patients with retro-cochlear hearing loss caused by an acoustic neuroma (Group 2). Narrow-band noise signals at four differe nt frequencies (0.5 to 4.0 kHz) were used. In the cochlear hearing-impaired subjects the slopes of the level-loudness functions fended to increase wit h increasing hearing loss, indicating positive recruitment, whereas, the mu ch shallower slopes associated with retro-cochlear lesions were presumed to reflect negative recruitment. The graphic representation of the iso-loudne ss functions revealed a different dynamic range between Group 1 and 2 with the ability to discriminate small differences of stimulus levels reduced in the presence of an acoustic neuroma. Category loudness scaling has been sh own to be a valuable tool describing the individual perception of sound in a qualitative and quantitative manner. Furthermore, the method can be emplo yed as an indicator of recruitment without any restrictive preconditions. F or this reason the categorial loudness scaling can be a desirable method fo r supplementing the audiological diagnosis of a retro-cochlear hearing impa irment through the frequency-specific description of a usable hearing-field and its dynamic range.