| 摘要 |
A telecommunications terminal (100, fig.1) such as a mobile telephone, a speaker phone, a portable radio or a vehicle radio may have to operate in a noisy environment such as an airport, a railway station, a bust street or a noisy factory. In the present invention, the terminal includes a microphone (111, fig.1) and a loudspeaker (110, fig.1). The terminal also includes a noise energy estimator (117, fig.1) for estimating audio noise energy received by the microphone and an adaptive enhancement filter (108, fig.1) for applying to the received signal in a selected audio frequency band a gain which is greater than the gain applied to audio frequencies outside the selected band, the gain applied being a function of the audio noise energy input. In the enhancement filter (108, fig.1) the audio channel is split into two branches, including a bandpass filtered branch (204 fig.2) for frequencies of e.g. 2 - 3 kHz. The gain applied to the bandpass filtered branch varies in accordance with the measured ambient noise. The overall gain may be kept substantially constant. The system does not significantly increase the overall audio power and avoids distortion. |
