Development of Stepped Notch Ultrasonic Speaker Capable of Concentrating Sound at Arbitrary Point Based on Huygens' Principle - 1st Report: Proposal and Concept Verification -

The purpose of this study is to develop a super directional speaker with the parabolic reflector that can arbitrarily change the width of the reflected audible area. Conventional ultrasonic speakers have not been able to control the width of the audible area. In our previous study, we proposed the method of radiating sound to a parabolic reflector and arbitrarily changing the width of the reflected sound. In this method, the sound must be emitted from the focal point of the parabola. This sound is called a point source. To generate this point source, the Curve Shaped Speaker, in which each speaker element is arranged on a circular arc, has been proposed. However, this method requires a mechanism to change the curvature of the parabolic reflector and a mechanism to change the position of the point sound source (focal point), which requires a large space. Therefore, this study proposes an ultrasonic speaker system that keeps the curvature of the parabolic reflector constant while keeping the width of the reflected sound constant. To achieve this, this paper proposes a speaker system in which the central angle of the audible area, which fans out from the focal point to the parabolic reflector, can be controlled (called a “Stepped Notch Shaped Speaker”) based on Huygens' principle. Basic experimental results confirm that the step-notched loudspeaker can concentrate sound at an arbitrary position with high sound pressure.