用声卡进行数据采集，产生一正弦波，计算机通过扬声器把此正弦波用声音的形式发出；用话筒，把声音采集，然后比较这两种信号(Using sound card to collect data and produce a sine wave, the computer sends out the sine wave in the form of sound by means of loudspeaker, and uses microphone to collect the sound, then compares the two signals to get the final result.)