- 2078 Chaitra · 5 marks
Noise vs interference vs distortion
Short answer
Noise is random, additive, always present, from thermal and natural sources, and cannot be removed completely. Interference is structured, man-made signals from other transmitters, reducible by filtering. Distortion is deterministic waveform change due to the system, vanishes without signal, and can be colected by equalisation.
Differentiate among noise, interference and distortion.
Noise, interference and distortion all degrade a received signal, but they differ in origin and in how they can be reduced.
- Noise: unwanted, random electrical signals that add to the wanted signal. Sources: thermal (Johnson) noise in resistors, shot noise in devices, atmospheric, cosmic and man-made noise. Example: hiss in a radio, snow on a TV screen.
- Interference: contamination by unwanted signals from other man-made transmitters or systems, usually having a definite structure and frequency. Example: a neighbouring radio station heard in the background, crosstalk between telephone lines.
- Distortion: change in the shape of the signal caused by the imperfect response of the system itself (non-flat amplitude, non-linear phase, non-linearity). Example: a square pulse becoming rounded after a band-limited channel.
| Basis | Noise | Interference | Distortion |
|---|---|---|---|
| Nature | Random, unpredictable | Signals from other sources, structured | Deterministic alteration |
| Source | Natural and device physics | Other transmitters, crosstalk | System/channel response |
| Present without signal? | Yes | Yes | No, disappears with signal |
| Spectrum | Wideband (white) | Narrow, at specific frequencies | Within/around signal band |
| Mathematical effect | Additive | Additive | , not |
| Reduction | Filtering, low-noise amps, more power, coding | Filtering, shielding, frequency planning | Equalizers, linear design, pre-distortion |
Key point: distortion can in principle be undone by an inverse system (equalizer), because it is a deterministic function of the signal; noise cannot be removed completely, only reduced, because it is random.
✓ Answer checked by Claude Opus 5.5 (high effort)
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