说明：  大作业4：信号的分数倍转换 本次作业每组有两个音频文件：music-28.wav和music-50.wav。 music-28.wav表明采样频率为28kHz采样（单声道，16位）的音乐文件，music-50.wav表明采样频率为50kHz采样（单声道，16位）的音乐文件，每个文件都加有单载波干扰。要求将这两个文件分别读出，将采样频率转换为16kHz，然后通过声卡播出。注意，声音不能失真不能含有单载波干扰。
(Great Job 4: scores of times signal conversion The work of each group has two audio files: music-28.wav and music-50.wav. music-28.wav show a sampling frequency of 28kHz sampling (mono, 16) of music files, music-50.wav show a sampling frequency of 50kHz sampling (mono, 16) of music files, each file plus a single-carrier interference. Requested that two documents were read out, the sampling frequency is converted to 16kHz, and then broadcast through the sound card. Note that the sound is not distorted can not contain single-carrier interference.)