5

代码说明：

说明：  把信号用数字或符号表示成序列，通过计算机或通用（专用）信号处理设备，用数值计算方法进行各种处理，达到提取有用信息的目的。(The signal using numbers or symbols into a sequence that, through the computer or general-purpose (dedicated) signal processing equipment, numerical calculation using a variety of treatment methods to achieve the purpose of extracting useful information.)