Implementation of a Parametric Ultrasonic Receiver Using Multilayer Lead Zirconate Titanate for a Feasibility Study of an Ultrasonic-Beam-Focused Hearing Aid

We demonstrated that focusing an ultrasonic beam on the eardrum can overcome the high-frequency sensitivity limitations and acoustic distortion of conventional hearing aid receivers. Multilayer PZT was used for an ultrasonic receiver that operates at low voltage and enters the external auditory canal, and a 3 mm radius radiator was designed to radiate the focused parametric acoustic signal to the center of the eardrum based on an acoustic analysis according to the frequency. To this end, an ultrasonic earphone consisting of a radiator attached to multilayer PZT and a 130 kHz parametric ultrasonic modulator was implemented; vibration and sound pressure were measured using a laser vibrometer and a tube-type microphone. The proposed parametric ultrasonic receiver generates an average sound pressure of 70 dB SPL at a frequency of 1~10 kHz with a 10 Vpeak applied voltage; this was implemented to provide a higher output in the range of 5 kHz and above, which is difficult to cover with existing receivers.