Directivity of circular transverse vibrating plate type aerial ultrasonic source with a truncated cone shaped reflective plate

Abstract

A highly directed sound source is necessary to achieve high acoustic pressure (AP) in the far field. For this purpose, we investigate the directivity of an ultrasonic source comprising a circular vibrating plate (VP) and a truncated conical reflector. This source radiates highly directed aerial ultrasonic waves by having the VP driven transversely by a longitudinal vibrator and the reflector installed near the VP. The results show that highly directed sound waves form on the central axis of the VP. Herein, we investigate the AP distribution on a plane parallel to the VP. We then examine the directivity by measuring the full width at half maximum (FWHM) of the AP distribution. We measure the phase distribution on planes both parallel and perpendicular to the VP. The results show that the AP on the plane parallel to the VP is high near the VP centerline. The FWHM of the radiated sound waves measured 1 m from the VP is roughly 100 mm. The planar phase distribution shows a phase-aligned part near the VP centerline on the plane parallel to the VP. In addition, we confirm the spread of the sound waves from the phase on the plane perpendicular to the VP.