提供采样频率、窗口长度和加载信号。单击信号上的任意点。程序在点的两侧创建一个给定长度的窗口, 并计算并显示 FFT。(Provide the sampling frequency, window length and load the signal. Click on any point on the signal. Program creates a window of given length on either side of the point and calculates and displays FFT.)