Gradient Microphones

Abstract

The response-frequency and directional characteristics of gradient microphones from zero to nth order have been obtained. Higher order unidirectional microphones have also been developed. The directivity increases with the order which means a corresponding discrimination against random sound. The accentuation of the low frequency response, when the distance from a small source is less than a wave-length, increases with the order and the wave-length. This feature may be used to obtain high discrimination against distant sounds in a close talking microphone. The amount of discrimination increases with the order of the microphone.

Study of nonuniform linear differential microphone arrays with the minimum-norm filter

“…Unlike the conventional way that forms an Nth-order DMA by subtractively combining the outputs of two DMAs of order N À 1 [3][4][5][6][7], this method works in the short-time Fourier transform (STFT) domain as illustrated in Fig. 1.…”

“…Secondly, the response of an Nth order DMA has an effect of high-pass filtering and, therefore, its frequency response has to be properly compensated to process broadband signals. Although much effort has been devoted to them in the literature [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], these issues have not been fully addressed.…”

“…Moreover, DMAs are generally small in size and can be integrated into small communication devices such as smartphones, tablet computers, bluetooth headphones, and hearing aids. With these advantages, the design of DMAs has attracted a significant amount of interest [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…The basic idea of such arrays can be dated back to the 1930s when the directional ribbon microphones were invented [1,2]. Since then, DMAs have been used in solving many important problems in voice communication such as noise reduction and spatial sound recording.…”

Unidirectional acoustic probe based on the particle velocity gradient

“…Since 1932, extensive research has been undertaken on cardioid unidirectional microphones based on the first-order sound pressure gradient principle. [1][2][3][4][5][6] Over the following decades, researchers also began investigating second and higher order unidirectional microphones in order to enhance directional characteristics. 7,8 With the emergence of particle velocity sensors, the development of unidirectional probes based on the particle velocity gradient became feasible.…”