Investigations in acoustics, electroacoustics and signal processing

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My aim is to support the audio engineering community with basic research in acoustics, electroacoustics, measurement tools, and signal processing.  It is motivated both by personal curiosity and a genuine desire to help the industry.  This area is multidisciplinary, drawing on physics, mathematics and engineering.  Projects chosen for study derive from contact with prospective graduate students, industry, and personal priorities.   Completed research is (a) a study of the benefits of a high magnetic field strength (high Bl) on the power efficiency of normal cone loudspeakers, especially the combined benefits of high Bl in combination with switching or class-D amplifiers, (b) a study of the acoustic centre of normal sealed-box monopolar loudspeakers, particularly relevant to understanding how loudspeakers act in rooms, and (c) measurement of acoustic surface impedance with a new, accurate and rapid method.  Newly-proposed loudspeaker research will be chosen from several areas: (i) further work on acoustic surface impedance measurements, (ii) a study of the acoustic nonlinearities that are responsible for the poor performance of concentric speaker systems, involving the acoustics of moving boundaries, and (iii) study of viscoeleastic loudspeaker damping and the inertia of the moving air near the cone.   For over 20 years a colleague and I have worked on dither, which is the addition of noise to a quantizer to turn its distortion and noise modulation into benign low-level noise.  These studies have influenced the way digital audio has flourished.  Properly dithered systems have infinitely fine signal resolution and no noise modulation, becoming truly analog in their behaviour.  We will apply these same concepts to image processing, extending these studies to different forms of dither in multi-bit image processing as well as partial dithering in low-bit half-toning.   An ongoing peripheral project is a study of the propagation of acoustic waves in concrete and other civil engineering solids, in order to detect flaws and cracks.