Yeonhee Oh , pp. 64. ING/School of Engineering, 2010.
This thesis addresses the following problem: which type of geometric arrangement and position of microphone arrays can improve the quality of a speech source well in a conference room. A speech source picked up at the microphone array is corrupted by a surrounding noise and reverberation. The extended version of Wiener filter beamformer in the subband domain is implemented because of the reverberation in the room. The implemented filter banks are used to transfer the signals receiving at the microphone array into subband sequences, and recover the signal in time domain from sequences in subband. The following geometric arrangements of the microphone array are analyzed: linear, parabolic, elliptical and circular shapes. Since a microphone array is usually arranged in a linear geometry, it is used as a reference to compare the results from arranging the microphone arrays in other geometries. It is estimated when the microphone array is arranged linearly, whether or not the locations of it affect on the measures of noise and interference suppression, and speech distortion. Also, the effects of geometric arrangements of microphone arrays are evaluated.
Results show that when the microphone array is placed closer to the speech source, it has better performances in noise and interference suppression and speech distortion. The microphone array arranged as one of geometric shapes does not improve the qualities of the speech source in both of noise and interference suppression.
As a further work, it can be considered that spacing between elements consisting of a microphone array varies depending on the frequencies. A microphone array can be arranged in three dimensions. For instance, geometric arrangement shapes for the microphone array can be a sphere, cube, cone or cylinder.