Question

Companding is used in PCM in order to ________.

• A. keep the quantization noise low for low-amplitude segments of a signal
• B. avoid quantization noise
• C. reduce the effect of impulse or channel noise
• D. reduce the complexity of the PCM system

Hint:

Companding improves SNR for small signals by redistributing quantization levels non-uniformly.

Answer 1

The Correct Option is A

Companding (Compression + Expanding) is a nonlinear technique used in PCM systems to:
- Apply a nonlinear transformation before quantization (compression).
- Reverse the transformation at the receiver (expanding).
Purpose: - Low amplitude signals get more quantization levels → lower noise.
- High amplitude signals get fewer levels but already have higher energy → noise less noticeable.
Common companding laws:
- μ-law (used in North America)
- A-law (used in Europe)