说明：  信号频谱分析 1. 观测已知方波信号、正弦波信号的频谱 分析频率为4KHz、8KHz的占空比为50 的方波信号、正弦波信号的频谱。记录所得频谱图。 2. 观测实时模拟信号（语音）的频谱 用音频设备采集一段语音，将语音存为.wav格式。对wav文件作分段傅里叶变换分析。语音是分音节的，应把它分段分析，而且实际运用中的数字信号处理的FFT的点数是有限的，一般只能达到千点。用傅里叶反变换IFFT，从频域恢复信号。画出频谱图和语音波形图
(Signal spectrum analysis 1. Observing a known square-wave signal, sine wave signal frequency spectrum analysis 4KHz, 8KHz for the 50 duty cycle square wave signal, sine wave signal frequency spectrum. The recorded frequency spectrum. 2. Observing real-time analog signal (voice) of the spectrum collected with the audio devices section of voice, voice saved as. Wav format. Wav file of the sub-Fourier transform analysis to make. Speech is divided into syllables, it should be sub-analysis, and practical application of digital signal processing of the FFT points is limited, generally only reach 1000 points. Fourier inverse transform IFFT, to restore the signal from the frequency domain. Draw maps and voice waveform spectrum)