Middle ear and cochlear disorders result in different DPOAE growth behaviour: implications for the differentiation of sound conductive and cochlear hearing loss
Abstract
Input/output functions of distortion product otoacoustic emissions (DPOAE I/O-functions) give an insight into the compressive, non-linear sound processing of the cochlea. With an inner ear dysfunction a steeper I/O-function is observed. Due to the linear sound processing of the middle ear, one can assume that the DPOAE growth behaviour remains unaltered with a sound conduction dysfunction. If that is true, a differentiation between middle and inner ear dysfunction will be possible by using the slope of DPOAE I/O-functions as a means for assessing cochlear compression. In order to test that hypothesis, DPOAE I/O-functions were recorded in a wide primary tone level range at up to 8 f2 frequencies between 2.0 and 8.0 kHz (15 dB SPL < L2< 60 dB SPL; L1=0.46 L2 + 41 dB SPL; f2/f1=1.2) in guinea pigs in which middle (saline solution in the bulla) and inner ear (exposure to loud broadband noise) disorders were induced. Middle ear dysfunction resulted in a reduction of the DPOAE amplitude independent of the primary tone level. Consequently, DPOAE growth behaviour was not affected. In contrast to that, during cochlear impairment, steepened DPOAE I/O-functions were observed reflecting loss of compression of the cochlear amplifier. Accord...Continue Reading
References
Citations
Estimation of Minor Conductive Hearing Loss in Humans Using Distortion Product Otoacoustic Emissions
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