An evoked response audiometer is disclosed in which the patient is presented with a continuous auditory signal which is amplitude modulated and the evoked brain potentials of the patient (EEG) are recorded. The potentials are amplified and filtered and are averaged over a number of sampling periods to improve the signal to the noise ratio. The averaged signals are then analysed to determine the amplitude and phase of the main components of the response to determine whether phase locking has occurred. The phase of the main components is then plotted against variation of the modulating frequency and the gradient of the plot provides the latency of the response from which neurological and other factors of significance to the hearing of the patient may be determined. The sound pressure level of the auditory signal is also varied and the amplitude and phase of the response plotted against these changes to provide an indication of the sensitivity of the hearing of the patient.
Evoked response audiometer