How-Does-Active-Noise-Cancelling-(ANC)-Work
April 15, 2024

How Does Active Noise Cancelling (ANC) Work?

Introduction

Active noise cancellation (ANC) is a technology that aims to reduce or eliminate unwanted ambient sounds. Here’s how it works:

  1. Phase Cancellation Principle:
    • ANC relies on the principle of phase cancellation. When two sound waves are 180 degrees out of phase (i.e., their peaks and troughs align), they cancel each other out.
    • Imagine adding +1 and -1 together; the result is zero. Similarly, ANC creates “anti-noise” by inverting the background noise signal and adding it to your music or audio output.
    • The anti-noise signal cancels out the actual background noise at the point where it reaches your ears.
  2. Microphone Placement and Accuracy:
    • ANC headphones have built-in microphones that capture ambient sounds.
    • These microphones must accurately sample the noise to provide effective cancellation.
    • The phase of the cancellation waveform leaving the headphone drivers needs to perfectly align with the phase of the noise when it reaches your ears.
    • Achieving this precise alignment is challenging, but even with fine-tuning, ANC systems typically achieve 20–40 dB of noise reduction.
  3. Types of Noise-Canceling Technology:
    • Not all ANC implementations are equal. Different types of ANC technology exist:
      • Feedforward ANC: Microphones are placed outside the ear cups to capture external noise. This type works well for constant, droning sounds.
      • Feedback ANC: Microphones are placed inside the ear cups, capturing the sound that leaks from the headphones. It’s effective for low-frequency noise.
      • Hybrid ANC: Combines feedforward and feedback methods for better overall noise reduction.
      • Adaptive ANC: Adjusts cancellation based on the environment and noise level.
      • Single vs. Multi-Microphone Systems: Some headphones use multiple microphones for better accuracy.
      • Quality of Ear Pads: Headphones with ear pads that fully encompass the ears provide better passive isolation and enhance ANC performance.
  1. Limitations:
    • ANC works best on constant, droning sounds (e.g., airplane engines, air conditioning).
    • Quick, irregular sounds (like music or people talking) are challenging to cancel because they occur before the headset can calculate how to counteract them.
    • Achieving a 100% cancellation rate is impossible due to practical limitations.

Is ANC Worth It?

  • Benefits:
    • ANC significantly reduces background noise, making it ideal for travel, work, or noisy environments.
    • It enhances audio quality by allowing you to hear your music or calls without interference.
    • Reducing noise can also reduce listening fatigue.
  • Considerations:
    • ANC headphones tend to be more expensive due to the technology involved.
    • The battery life may be slightly shorter due to the active noise-cancelling circuitry.
    • Some people prefer passive noise isolation (using well-fitting ear pads) over ANC.

In summary, if you frequently find yourself in noisy environments or want to enjoy high-quality audio without distractions, ANC headphones are worth considering.


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