说明：  程序是对输入的语音信号添加已知信噪比的噪声，输入是纯净的语音信号和信噪比，输出是加噪后的语音信号。后半部分是验证前面所加信噪比是否正确的程序
(Procedure is to add the input speech signal noise ratio of the noise is known, the input speech signal and pure noise ratio, after output speech signal plus noise. Latter is to verify whether the previously added the correct procedure SNR)