In digital signal processing (DSP), noise refers to any unwanted or random signal that interferes with the original signal. It can originate from various sources—both external (physical environment) and internal (processing system).

Common Sources of Noise in DSP

1. Quantization Noise

Caused during analog-to-digital conversion (ADC) when continuous values are approximated to discrete levels.
The difference between actual analog value and the quantized digital value.
Depends on bit resolution of ADC.

Higher resolution = lower quantization noise

2. Rounding and Truncation Errors

Occur in finite-precision arithmetic (e.g., fixed-point DSPs).
Every multiplication, division, or addition can introduce rounding errors.
Accumulates in long filter operations or transforms like FFT.

3. Electromagnetic Interference (EMI)

External electromagnetic fields from nearby devices (motors, Wi-Fi, radio transmitters).
Affects analog front-end (sensor or amplifier) before digitization.

Common in industrial and automotive environments.

4. Thermal Noise (Johnson-Nyquist)

Generated by resistors and semiconductors due to random electron motion.
Present in analog front-end circuits (before digitization).

Inherent and unavoidable in physical components.

5. Power Supply Noise

Fluctuations or ripple in power lines can induce noise in analog and digital circuits.
Especially critical in high-gain analog front-ends and ADCs.

6. Sampling Jitter

Variation in sampling time intervals.
Introduces errors in reconstructing the original analog signal.

Mostly caused by clock instability in ADC systems.

7. Algorithmic Noise

Artifacts from improper DSP algorithm design.
Examples: leakage in FFT, side lobes in filters, or unstable IIR filters.

8. Interference and Crosstalk

Signal leakage between channels in multi-channel systems.
Common in wired communication systems or shared buses.

9. Sensor Noise

Inherent noise in sensors (e.g., microphone hiss, thermal noise in image sensors).
Affects the input signal before it even reaches DSP.

Summary Table

Source	Type	Affects
Quantization noise	Digital	ADC conversion
Rounding/truncation	Digital	Arithmetic operations
Thermal noise	Analog	All physical circuits
EMI	External	Analog/digital input
Power supply noise	Analog/system	All system levels
Sampling jitter	Timing/clock	ADC/DAC accuracy
Algorithmic noise	Software/design	Filtering/FFT errors
Sensor noise	Hardware	Input signal
Crosstalk/interference	Hardware/layout	Multi-channel systems

What are common sources of noise in digital signal processing?