Available at: https://digitalcommons.calpoly.edu/theses/3047
Date of Award
6-2025
Degree Name
MS in Electrical Engineering
Department/Program
Electrical Engineering
College
College of Engineering
Advisor
Vladimir Prodanov
Advisor Department
Electrical Engineering
Advisor College
College of Engineering
Abstract
Parametric acoustic arrays are directional loudspeakers that operate using ultrasonic carriers to project sound within a narrow beam. Input audio is first modulated onto an ultrasonic carrier and transmitted through air, where it self-demodulates into audible frequencies in the far field.
This thesis introduces a method for preprocessing audio into scaled quadrature signals using a passive analog polyphase filter. These signals are modulated using microcontroller-generated waveforms to create quadrature ultrasonic pulse-width modulation (PWM) signals. The modulated outputs are combined through a wired-OR summer, producing single-sideband ultrasonic content at the desired frequency of 40 kHz. This signal is amplified through high-efficiency switching amplifiers and transmitted via an array of 5x6 ultrasonic transducers (5cm x 6cm). Upon propagation through air, the acoustic signal self-demodulates into highly directional audible sound.
Experimental results demonstrated audible and focused audio within a beamwidth of less than 40°, with effective transmission of at least 4 meters. These results confirm the viability of the proposed modulation pipeline for compact, directional sound projection using parametric arrays.