Patent ID: 6243323
Filing Date: 2001-06-05
Classification: G01S

Abstract:
A method for producing ultrasonic sound waves with an ultrasonic transducer to realize reduced audible noise, said method comprising the steps of:generating an electrical pulsed signal at an ultrasonic frequency;generating a modulation envelope having a contour that gradually changes from a low amplitude to a high amplitude and then back to a low amplitude;modulating said pulsed signal with said modulation envelope such that said pulsed signal bas an amplitude that varies according to the modulation envelope, wherein said step of modulating comprises amplitude modulating said pulsed signal based on a substantially sine wave contoured modulation envelope;generating a transducer drive signal based on said modulated pulsed signal; andapplying the transducer drive signal as an input to an ultrasonic transducer to produce ultrasonic sound waves with reduced audible noise effects.