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.)