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Engineering Brief

Virtual Microphones: Optimum Real-Time Demodulation of Phase Modulated Ultrasound

Authors: Ritter, Tom; Merkel, Tobias; Lühmann, Hans-G.

AES Convention 132 · Paper 43 · April 2012

Abstract

The project “Virtual Microphones” aims to replace conventional audio microphones by a system consisting of ultrasonic sensors. The fundamental physical principle utilized is that ultrasonic waves are phase-modulated when superimposed by audio waves. Due to the physical relationships the phase changes of the ultrasonic carrier are very small. The precise demodulation of the audio signal was in the focus of the investigation among other measures, like providing a very stable carrier frequency or the focusing of the ultrasound beam on the receivers. Several methods of demodulation for phase-modulated signals are compared. The comparatively low resulting signal-to-noise ratio after the demodulation required further signal processing in form of noise reduction to be investigated and its performance accessed.

Details

Published in
AES Convention 132
AES Convention
132
Paper number
43
Publication date
April 6, 2012
Affiliation
Beuth University of Applied Sciences Berlin; Lütronic Elektroakustik GmbH (See document for exact affiliation information.)
Type
Engineering Brief