| 摘要 |
A communications device, such as a cellular telephone handset (10), and a method of operating the same to suppress noise in audio information such as speech, is presented. The handset (10) includes a digital signal processor (DSP) (30) having program memory (31) for controlling the DSP (30) to apply a hierarchical lapped transform to the input digital sequence. The hierarchical lapped transform decomposes the input sequence into coefficients representative of plurality of sub-bands corresponding to critical bands of the human ear. Each coefficient is modified by a noise suppression filter operator, based upon a ratio of an estimate of the noise power to an estimate of the signal power in the corresponding sub-band; clamping of changes in the noise power estimate over time, and use of a decaying signal envelope estimate, eliminate distortion in the processed signal. Musical noise is eliminated by using a minimum gain value in each sub-band. Inverse transformation of the modified coefficients provides the filtered time-domain output signal. Improved noise suppression is provided, in a manner that may be readily and robustly performed by fixed-point digital signal processors.
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