说明：  主动降噪（主动噪声控制），又称为有源噪声控制。本系统一般由初级声源、自适应控制器、次级声源和误差传感器组成。其特点是控制器带反馈，并具有自适应控制算法，控制器多为数字控制器。这种系统适用的范围宽，相对灵活，但其结构复杂，实现难度加大，成本增加。并进行matlab仿真。
(Active Noise Reduction (Active Noise Control), also known as active noise control. The system consists of a primary sound source, adaptive controller, secondary source and the error sensor. It features a controller with feedback and adaptive control algorithm, the controller mostly digital controller. This system is suitable for a wide range, relatively flexible, but its structure is complicated, difficult to achieve and increase costs. And matlab simulation.)