美国消除噪声技术公司(NCT)采用一种过程控制微机系统既可以抑制烟囱的废气噪声又可抑制机器引起的振动。该公司的NCT 2000系统以分析、预测其波形结构然后产生一“抗噪声”信号——与振源波形相位正好相差180°的波形以消除低频的振动与噪声,这个消波干扰使原始的振动和噪声被一“镜象”信号所消除,结果使二个波合成为零。NCT公司称此为“有源”法消除噪声。 NCT uses a process control microcomputer system to both suppress emissions from chimneys and suppress machine-induced vibrations. The company’s NCT 2000 system analyzes and predicts its waveform structure and generates an “anti-noise” signal - a waveform that is exactly 180 ° out of phase with the source waveform to eliminate low-frequency vibrations and noise that cause the original vibration And the noise is canceled by a “mirror” signal, resulting in the two waves becoming zero. NCT called the “active” method to eliminate noise.