Electrical audio signal processing systems and devices – Directive circuits for microphones
Patent
1994-12-06
1997-03-11
Kuntz, Curtis
Electrical audio signal processing systems and devices
Directive circuits for microphones
381 94, 381 13, H04R 300
Patent
active
056109911
ABSTRACT:
A noise reduction system and device, and a mobile radio station. Known is a combined Zelinski-spectral subtraction system (1) for noise reduction in a combined speech signal (a(t)) in which signals are recorded with a plurality of microphones (5, 6, 7), using a Wiener filter (10) for estimation of the combined speech signal (a(t)'). In the known system (1) sums and differences of all combinations of speech signals are formed, it being assumed that the differences comprise noise only. Furthermore, a two stage estimation process is carried out, giving rise to considerable estimation errors. An alternative combined Zelinski-spectral subtraction system (1) is proposed, giving rise to fewer estimation errors and being more efficient from a computational point of view. In the Zelinski system, spectral subtraction is carried out on a combined cross spectrum (.PHI..sub.cc). Then, on a speech segment by speech segment basis, filter coeffients for the Wiener filter (10) are determined from a combined auto power spectrum (.PHI..sub.ac) and the thus corrected combined cross power spectrum (.PHI..sub.cc '). The spectral subtraction is carried out on a lower part of the frequency range only, thereby not introducing unneccesary artefacts.
REFERENCES:
R. Zelinski, "A Microphone Array With Adaptive Post-Filtering For Noise Reduction In Reverberant Rooms", 1988 International Conference on Accoustics, Speech and Signal Processing, Apr. 11-14, 1988, New York City, pp. 2578-2581.
K. Kroschel, "Enhancement Of Speech Signals Using Microphone Arrays", Digital Signal Processing, Proceedings of the International Conference, Florence, Italy, 4-6 Sep., 1991, pp. 223-228.
R. N. Bracewell, "The Fourier Transform and Its Applications", 1986, pp. 356-384.
R. E. Blauht, "Fast Algorithms for Digital Signal Processing" Addison Wesley, 1987, pp. 352-362.
P. De Souza, "A statistical Approach to the Design of an Adaptive Self-Normanlizing Silence Detector", IEEE Trans. on Acoustics, Speech and Signal Proceesing, vol. ASSP-31, No. 3, Jun. 1983, pp. 678-684.
Kuntz Curtis
Oh Minsun
Slobod Jack D.
U.S. Philips Corporation
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