| 摘要 |
<p>In a method and apparatus for improving sound quality in a digital cellular radio system receiver a voice activity detector (50) uses an energy estimate (from 210) to detect (in 230) the presence of speech in a received speech signal in a noise environment. When no speech is present the system attenuates the signal (by 240,270) and inserts low pass filtered white noise (by 270). In addition, a set of high pass filters (in 260) are used to filter the signal based upon the background noise level (from 220). This high pass filtering is applied to the signal regardless of whether speech is present. Thus, a combination of signal attenuation (in 270) with insertion of low pass filtered white noise (from 250) during periods of non-speech, along with high pass filtering (in 260) of the signal, improves sound quality when decoding speech which has been encoded in a noisy environment. <IMAGE></p> |
