Further evaluation of a model of loudness perception applied to cochlear hearing loss

This paper describes further tests of a model for loudness perception in pe ople with cochlear hearing loss. It is assumed that the hearing loss (the e levation in absolute threshold) at each audiometric frequency can be partit ioned into a loss due to damage to outer hair cells (OHCs) and a loss due t o damage to inner hair cells (IHCs) and/or neurons. The former affects prim arily the active mechanism that amplifies the basilar membrane (BM) respons e to weak sounds. It is modeled by increasing the excitation level required for threshold, which results in a steeper growth of specific loudness with increasing excitation level. Loss of frequency selectivity, which results in broader excitation patterns, is also assumed to be directly related to t he OHC loss. IHC damage is modeled by an attenuation of the calculated exci tation level at each frequency. The model also allows for the possibility o f complete loss of IHCs or functional neurons at certain places within the cochlea ("dead" regions). The parameters of the model (OHC loss at each aud iometric frequency, plus frequency limits of the dead regions) were determi ned for three subjects with unilateral cochlear hearing loss, using data on loudness matches between sinusoids presented alternately to their two ears . Further experiments used bands of noise that were either I-equivalent rec tangular bandwidth (ERB) wide or 6-ERBs wide, centered at 1 kHz. Subjects m ade loudness marches for these bands of noise both within ears and across e ars. The model was reasonably accurate in predicting the results of these m atches without any further adjustment of the parameters. (C) 1999 Acoustica l Society of America. [S0001-4966(99)01707-5].