Definition: Active Noise Cancelling (ANC) is a technology that actively reduces or cancels out unwanted ambient sounds by generating sound waves with opposite phase to the incoming noise.
Principles:
- Destructive interference: When two sound waves of equal amplitude and opposite phase combine, they cancel each other out.
- Microphone capture: Microphones capture surrounding noise.
- Signal processing: A digital signal processor (DSP) analyzes the captured sound and generates an anti-noise signal.
- Anti-noise generation: The anti-noise signal is a mirrored image of the original noise, but inverted in phase.
- Speaker emission: Speakers emit the anti-noise signal, which combines with the original noise, leading to destructive interference and reduced noise levels.
Effectiveness:
- Most effective against low-frequency and continuous noises like engine hum, traffic noise, and air conditioning.
- Less effective against sudden or impulsive sounds like door slams or sharp bursts.
Components:
- Microphones: Capture ambient noise.
- Digital signal processor (DSP): Analyzes and generates anti-noise signals.
- Speakers: Emit anti-noise signals.
Types of ANC:
- Feedforward ANC: Uses external microphones, effective for low-frequency noise.
- Feedback ANC: Uses internal microphones, effective for mid- and high-frequency noise.
- Hybrid ANC: Combines both approaches for broader noise cancellation.
Applications:
- Headphones and earphones
- Aviation: quieter cabins
- Automotive: reduced driver stress
- Office environments: improved focus
- Sleep environments: better sleep quality
Limitations:
- Not effective against all types of noise.
- Can create a feeling of isolation.
- Requires power source.
- Expensive for high-end implementations.
Future of ANC:
- Adaptive ANC: personalized noise cancellation based on environment.
- Integration with AI and spatial audio: immersive soundscapes.
- Wider applications: hearing aids, noise barriers, active vibration cancellation.
See also:
- Passive noise cancelling
- Soundproofing