Abstract: Hearing faculty test apparatus, for use in relation to the inner ear by way of the so-called cochlear echo, repeatedly applied a linearly balanced set of acoustic stimuli to the ear, individually sums each related set of responses to the stimuli set, interrogates each sum to detect components above a predetermined threshold, and averages sums on a selective basis depend on the interrogation. Preferably sums are passed for averaging only when whooly within the threshold. Also, averaging is preferably by use of two like averagers to which accepted sums are applied in alternating manner, with the two averages being fed to a correlator.

Abstract: A hearing faculty test and apparatus therefor is based on the findng that sound input to the ear gives rise to a returned wave from and related to the condition of the inner ear, this wave being detectable as an echo from the ear drum. The apparatus preferably comprises a sealing aural probe (1) housing transducers (2,3) respectively to project a repetitive transient sound by pulse generator (4) activation and to pick-up for detection (5) successive echoes by time-gating. Detected echoes are preferably averaged during processing (6) for display. The echo occurs about 5-20 ms after its sound and a maximum operating frequency of about 50 Hz is appropriate. A continuous sound input can be used with consequent echo interference detectable as rapid changes of acoustic impedance with sound input frequency. Another alternative can involve detection of the ear drum movement by returned waves.