Abstract
Parametric acoustic arrays (PAA) have progressed from specialized niche applications to commercially available audio solutions in the last two decades. Their primary advantage is their incredible directivity and their main disadvantage is low conversion efficiency of the primary ultrasonic waves into audible sound. This paper presents a noise analysis of a practical implementation of a directional audio system. The system is comprised of a modulator, a D-class audio amplifier, and an emitter consisting of 97 commercially available piezoelectric ultrasonic transducers. The designed system exhibited an uncomfortable level of idle noise at the maximum volume level. The analysis of the signal path and all the noise sources revealed that the most critical component was the modulator, and a solution was devised which provided a 16 dB improvement of the carrier to noise ratio.
Highlights
Parametric acoustic arrays (PAA) were first introduced by Westervelt in 1963 [1]
The results show that the CNR at the output of the modulator is improved by 18.5 dB, the CNR at the output of the power amplifier is slightly less improved, namely, by only 15.9 dB, since the noise generated by the power amplifier is not negligible anymore
The designed modulator amplifier system for a PAA resulted in good audio reproduction but exhibited noticeable acoustic noise when idle
Summary
Parametric acoustic arrays (PAA) were first introduced by Westervelt in 1963 [1]. Due to their high directivity and almost non-existent side lobes, many applications have been developed using PAA ranging from underwater applications [2, 3], sediment exploration [4], communications [3, 5, 6], to medical applications [7]. The two main challenges that each PAA system must overcome are the low conversion efficiency of the high frequency primary waves into secondary audible acoustic waves and the distortion of the desired signal. To achieve sufficient volume of audible sound, the volume of the ultrasonic beam has to be very high and the signal source needs to be sufficiently powerful. D-class amplifiers employ pulse width modulation (PWM), nearly lossless switches, and an appropriate filter to achieve the same results as linear amplifiers, but with much lower losses. These amplifiers feature high efficiency for resistive, reactive or combined loads. Measurement results and conclusions are given in the last two sections
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Informacije MIDEM - Journal of Microelectronics, Electronic Components and Materials
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
