CONVERSION
The Pulse Code Modulation (PCM) Technique
By Dr. Ernest Simo
3.0 Encoding Samples into Bits
Encoding Speech Signals
From standard landline telephony applications, highest practical frequency components of speech are considered to be around 4 KHz.
Applying Nyquist Rule, we shall, therefore, sample our speech waveform at the rate of 8000 samples per second.
In order to achieve excellent results on the subjective Mean Opinion Scoring (MOS) tests, 256 quantization levels are required. Each sample is thus represented by 8 bits, yielding a data rate of:
- 8000 samples/sec x 8 bit/sample=64,000 bps or 64 kbps.
ANALOG-TO-DIGITAL CONVERSION
The Pulse Code Modulation (PCM) Technique
© 1999 DR. ERNEST SIMO - SPACE2000