Radiated fields of thin and flexible high frequency loudspeakers

Abstract

Thin and flexible electrostatic loudspeakers have been constructed, which can be curved into different shapes. This allows some interesting geometries to be explored, at frequencies in the range 10 kHz to 100 kHz. The research has compared the radiated fields measured experimentally with those predicted using established theory. The theoretical approach uses a new geometrical formulation to more efficiently predict radiated field patterns, where the curved surface is considered as a series of elements at specific angles to the beam axis. These elements can be of increased width compared to previous methods, making the approach computationally efficient. It is also a more robust approach than the traditional impulse response methods, in situations where the source size is comparable to the radiated wavelengths in air. Predictions could be made for both continuous and transient excitation. A comparison between theory and experiment has demonstrated that interesting field patterns can be generated. For instance, focussed sound fields can be produced using concave shapes, with predictable focal positions which are not at the center of curvature. These and other geometries will be described.