Method for reducing noise in speech signals by adaptively contro

Details Method for reducing noise in speech signals by adaptively contro Method for reducing noise in speech signals by adaptively contro

1995-05-01

1997-09-16

MacDonald, Allen R.

Data processing: speech signal processing, linguistics, language

Speech signal processing

Recognition

704214, G10L 506

Patent

active

056689276

ABSTRACT:
A noise reducing method for speech signals is provided in which the probability of speech occurring is calculated by spectral subtraction of subtracting the estimated noise spectrum from the spectrum of the input signal, and the maximum likelihood filter is adaptively controlled based upon the calculated speech occurrence probability. Adjustment to an optimum suppression factor may be achieved depending on the SNR of the input speech signal, so that is it unnecessary for the user to effect adjustment prior to practical application. In addition, a method for detecting the noise domain is provided in which the value th employed for finding the threshold value Th.sub.1 for noise domain discrimination is calculated using the RMS value of the current frame or the value th of the previous frame multiplied by the coefficient .alpha., whichever is smaller, and the coefficient .alpha. is changed over depending on the RMS value of the current frame. Noise domain discrimination by an optimum threshold value responsive to the input signal may be achieved without producing mistaken judgement even on the occasion of noise level fluctuations.

REFERENCES:
patent: 5036540 (1991-07-01), Eastmond
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J.R. Deller et al., "Discrete-Time Processing of Speech Signals," 1987, pp. 506-516.
S. Furui, "Digital Speech Processing, Synthesis, and Recognition," 1989, pp. 91-98.
L.R. Rabiner, "Digital Processing of Speech Signals," 1978, pp. 158-161.
Boll, "Suppression of Acoustic Noise in Speech Using Spectral Subtraction," IEEE Trans. on Acoustics, Speech, and Signal Processing, 27(2):113-120, Apr. 1979.
G. Whipple, "Low Residual Noise Speech Enhancement Utilizing Time-Frequency Filtering," ICASSP-94, Apr. 19-22, 1994, pp. 5-8.
M. Nishiguchi, "Vector Quantized MBE with Simplified V/UV Division at 3.0 kbps," ICASSP-93, Apr. 27-30, 1993, pp. 151-154.
M.S. Ahmed, "Comparison of Noisy Speech Enhancement Algorithms in Terms of LPC Perturbation," IEEE Trans. on Acoustics, Speech, and Signal Processing, 37(1):121-125, Jan. 1989.

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