pcm编码们以话音信号为例来说明数字通信的基本原理。人类的语音信号的频率范围在300—3 400 Hz之间，留有一定余地，设话音信号最高频率为4 kHz，则根据奈奎斯特采样定理，将话音信号数字化所需要的采样频率为8 kHz，即采样周期为l25 US 0再把每个采样值用8位二进制数字编码，就把模拟话音信号转换成了数字信号。因此，一路话音信号转换成数字信号以后，比特率为8 x8 000 b／s：64 kb／s。将模拟信号用脉冲信号进行采样使其离散化并进行数字编码的过程称为脉冲编码调制，简称PCM，这是将模拟话音信号转换成数字信号的基本方法。

-PCM stands for Pulse Code Modulation. PCM technology is a means by which standard audio signals (which are represented by waveforms) are converted to digital audio signals (which are represented by 1 s and 0 s- much like computer data) with little, or no, compression. The method of audio conversion is used on most digital audio formats, including C