Differential Microphone Arrays

Abstract

Noise and reverberation can seriously degrade both microphone reception and loudspeaker transmission of audio signals in telecommunication systems. Directional loudspeakers and microphone arrays can be effective in combating these problems. This chapter covers the design and implementation of differential arrays that are by definition small compared to the acoustic wavelength. Differential arrays are therefore superdirectional arrays since their directivity is higher than that of a uniformly summed array with the same geometry. Aside from their small size, another beneficial feature of differential arrays is the inherent independence of their directional response as a function of frequency. Derivations are included for several optimal differential arrays that may be useful for teleconferencing and speech pickup in noisy and reverberant environments. Expressions and design details covering optimal multiple-order differential arrays are given. The results shown in this chapter should be useful in designing and selecting directional microphones for a variety of applications.