gms | German Medical Science

Human hearing is generally evaluated using behavioral tests that assess a) hearing thresholds at different frequencies – the pure tone audiogram, and b) the recognition of spoken words at supra-threshold levels – speech audiometry. In certain cases, most importantly in newborn infants, accurate behavioral audiometry is not possible, and objective tests of hearing are needed. The most widely used objective tests record the electrical responses of the brain, usually the brainstem responses to tones or chirps. In reviewing the current state of the field three principles can be noted:

1.

It is much faster to assess hearing thresholds when presenting multiple stimuli at the same time. Steady-state responses can be recorded to tones or chirps presented simultaneously at 4 different frequencies in each ear. In addition it is often helpful to record multiple responses to the same stimulus, e.g., both the onset response and the frequency-following response.

2.

Several new techniques have become available that make the delineation of thresholds objective. New statistical tests can identify a response without the need for subjective interpretation. Important in this regard are multiple-sample statistics to monitor the response as the recording progresses. New adaptive protocols can separately measure thresholds for each of the multiple stimuli.

3.

At present most objective audiometry is concerned with estimating the pure tone audiogram. We need to develop tests that also assess speech perception. We might consider the Mismatch Negativity to demonstrate discrimination, the response to the speech envelope to assess ongoing perception, and later endogenous waves of the auditory evoked potential to evaluate language.

Notes and references for this presentation are available at:

http://creatureandcreator.ca/?page_id=2080