Physical Constraints of High Resolution Acoustic Imaging in the 50 Hz - 15 kHz Frequency Range

Abstract

Identification and spatial detection of low frequency airborne sound sources, 50 Hz - 15 kHz, both generative and reflective, is not a clear cut task. The purpose of this paper is to give an overview of the physics and related mathematics that govern and acoustic imaging system. Most of the theory is borrowed from optics and is now applied to the field of acoustics. The paper highlights the relationship between wavelength and effective aperture. Other important issues addressed are field depth and resolving power, i.e. the point spread function. Chromatic aberration, spectral aberration, due to refraction is also discussed. The last issue is the comparison of a mirror/lens approach vs. a microphone array approach. Finally the paper concludes with a discussion of two applications. First it looks at architectural acoustics and second at a low frequency acoustic radar/sonar application.