A millimeter wave (MMW) radar sensor is employed in our laboratory to detect human\nspeech because it provides a new non-contact speech acquisition method that is suitable for various\napplications. However, the speech detected by the radar sensor is often degraded by combined noise.\nThis paper proposes a new perceptual wavelet packet method that is able to enhance the speech\nacquired using a 94 GHz MMW radar system by suppressing the noise. The process is as follows.\nFirst, the radar speech signal is decomposed using a perceptual wavelet packet. Then, an adaptive\nwavelet threshold and new modified thresholding function are employed to remove the noise from\nthe detected speech. The results obtained from the speech spectrograms, listening tests and objective\nevaluation show that the new method significantly improves the performance of the detected speech.
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