Training in ABR

Cochlear Microphonics for High Frequencies

10 mins
05 December 2016


The Cochlear Microphonic (CM) has been found to be dominated by hair cells located in close proximity to the recording electrode, near the base of the cochlear, regardless of stimulus frequency. Whilst a tone will generate greatest excitation of the basilar membrane at the characteristic frequency of the stimulus, it has been found that phase-rotation for hair cells at apical regions of the cochlear causes the vector sum of their CM to be much less than if the hair cells were orientated in the same direction, as occurs at the base of the cochlea. Therefore the CM is dominated by contributions of outer (and inner) hair cells within the basal region of the cochlea regardless of stimulus frequency. For more detail regarding these concepts, please see Withnell (2001).

The Eclipse uses 30 kHz sampled sound files, so this implies a maximum of 15 kHz sound stimulation is possible without risk of aliasing.  

References and caveats
Withnell,  R.H.  (2001)  Brief  report:  The  cochlear microphonic  as  an indication of outer hair cell function. Ear and Hearing, 22(1), 75-77.


Michael Maslin
After working for several years as an audiologist in the UK, Michael completed his Ph.D. in 2010 at The University of Manchester. The topic was plasticity of the human binaural auditory system. He then completed a 3-year post-doctoral research program that built directly on the underpinning work carried out during his Ph.D. In 2015, Michael joined the Interacoustics Academy, offering training and education in audiological and vestibular diagnostics worldwide. Michael now works for the University of Canterbury in Christchurch, New Zealand, exploring his research interests which include electrophysiological measurement of the central auditory system, and the development of clinical protocols and clinical techniques applied in areas such as paediatric audiology and vestibular assessment and management.

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