Abstract: A host controller for producing data from a computer for a programmable filter of a hearing aid to cancel feedback in which phase shift and gain control means as adjusted by the computer to generate a feedback cancellation voltage which is supplied to the hearing aid for summation of the feedback and feedback cancellation voltages by the hearing aid and in which the summed feedback and feedback cancellation voltages are returned to the host controller for further adjustment of said phase shift and gain control means until feedback has been cancelled. The host controller then transmits to the programmable filter the phase shift and gain control data necessary to cancel feedback.

Abstract: A hearing aid system comprises a hearing aid that is programmable so as to have optimum electro-acoustic characteristics for the patient and acoustic environment in which it is used. Selected optimum parameter values are programmed into an electronically erasable, programmable read only memory (EEPROM) which supplies coefficients to a programmable filter and amplitude limiter in the hearing aid so as to cause the hearing aid to adjust automatically to the optimum set of parameter values for the speech level, room reverberation, and type of background noise then obtaining. The programmable filter may be a digital equivalent of a tapped delay line in which each delayed sample is multiplied by a weighting coefficient and the sum of the weighted samples generates a desired electro-acoustic characteristic. Alternatively, the programmable filter may be a tapped analog delay line in which the sum of the weighted outputs of the taps generates the desired characteristics.

Abstract: Vestibular stimulation of a patient is effected by applying to the mastoid area metal, disk-like electrodes covered with insulating material, connected in a series resonant circuit including the electrodes and the body tissues therebetween, energizing the series resonant circuit by an ultrasonic frequency carrier, the frequency of which is determined by the series resonant circuit, and modulating the amplitude of the carrier at a frequency in the range from about 0.1 Hz to about 15 Hz to evoke a nystagmus response. The response is recorded as an indication of the condition of the vestibular system of the patient.