Auditory filters in sensorineural hearing impaired subjects

The study is devoted to determination of the shape of the
auditory filters in subjects with sensorineural hearing loss. Apart from the
classical sensorineural hearing loss, changes in the auditory filter shapes have
been analysed in the subject diagnosed with dead regions. The dead region is an
area on the basilar membrane over which the functioning of the inner hair cells
and/or neurones innervating them has ceased. This type of hearing impairment
means that the information on the sounds whose frequencies correspond to the
dead region of the basilar membrane are to a very limited degree if at all,
transmitted to higher levels of the auditory path. This transmission, if
happens, is performed through the auditory filters at the centre frequency other
than that of the signal. This phenomenon and the fact that in the dead region
the hearing loss is theoretically infinite, affect the transmittance of the
auditory filters. Results of the study reported here have shown that in general,
the subjects with sensorineural hearing loss develop broadening of the auditory
filter accompanied by reducing of its dynamics. This fact explains a
considerable decrease in speech intelligibility presented at a background of a
noise. In the subject with the dead regions the broadening of the filters was
the greatest in the region of the dead one. The results also indicate the lack
of correlation between the shape and width of the auditory filter and the shape
of the audiogram.