Although these methods can control and reduce the noise in most measurements, some techniques just prevent noise from entering the system, whereas others remove only extraneous noise from the signal.

虽然这些方法在大多数测量中能控制和减少噪声，但是一些技术只是防止噪声进入系统，而其他只是去除信号中的外来噪声。

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Any noise characteristic of the preamp circuit is attenuated along with the signal, unlike circuits where the volume control is before the input.

与一些音量控制置于输入端的电路不同，这个前级放大器的特征噪声能够随同信号一起衰减。

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Active noise control (ANC) is a new high technology integrated with acoustic, adaptive control and digital signal process and it has become the research focus center of noise control.

主动噪声控制是集声学、自适应控制及数字信号处理等技术为一体的高新技术，已成为国内外噪声控制界的研究热点。

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