How Do Noise Canceling Headphones Work?

In your quest for headphones, you may have encountered models featuring active noise canceling (ANC). But what exactly is ANC, and how does it operate?

For commuters or individuals who enjoy their music outside the confines of a soundproof room, there's no better enhancement than noise-canceling headphones. While many assume that spending more is the key to better sound quality, the truth may be only half of that equation. It's equally important to thwart external noise that could compromise or overpower your music before it reaches your ears. Several companies have ventured into the realm of active noise canceling (ANC) headphones, with some achieving remarkable proficiency, making it a primary selling point for their wireless headsets. But what makes noise-canceling headphones tick, and why is it such a noteworthy feature?

What is sound, and what is noise?

To comprehend the process of canceling noise, it's crucial to first grasp its nature. Sound, as perceived, essentially involves the compression and decompression of particles in the medium it travels through—in our context, the medium is air. Envision sound as a ripple propagating through the air. These moving particles induce subtle, rapid alterations in air pressure. The measurement of these fluctuations in air pressure is termed amplitude. Your ears and brain perceive and interpret these variations in pressure as sound. If you were to plot the amplitude over time, it would generate a waveform, akin to the illustration above. The greater the amplitude, the louder the sound, and the swifter the changes, the higher the pitch.

Sound can be either desired or undesired, pleasant or unpleasant. Noise is typically characterized as sounds that are unwanted, unpleasant, or excessively loud.

How do headphones cancel outside noise?

Your headphones employ a technique called "phase inversion" to generate "anti-noise" and effectively cancel ambient noise. Although the concept is straightforward, executing it correctly can be challenging.

Imagine taking two identical waves and aligning them, matching the peaks and troughs. When these waves synchronize, they are considered "in-phase," resulting in a combined wave with increased amplitude (louder sound).

Conversely, when the two waves are "out of phase," they subtract from each other. This occurs because the positive pressures of one wave counteract the negative pressures of the other, and vice versa. It's akin to attempting to add one and subtract one, ultimately leaving you with zero. This fundamental principle forms the basis of noise cancellation. But how is this applied in your headphones?

Do noise cancelling headphones work without music?

The short answer is, yes they do. Noise cancelling feature does not have to be activated with music playing simultaneously, and if you just want to lay back and enjoy some pure silence in your afternoon break, wearing your headphones without playing the music will also block all the noise.

Does noise canceling use microphones?

In order to create anti-noise, electronic headphones must constantly monitor and sample ambient noise using tiny built-in microphones. They “listen” to the ambient noise around you, and then the onboard electronics take it from there. In addition to playing your music, the headphones produce sound waves precisely opposite to the incoming ambient noise, effectively canceling it out. The goal is to ensure that what you primarily hear is the music emanating from your headphones, with minimal interference from external sounds.

However, in practice, achieving flawless noise cancellation is challenging and far from perfect. Consistent noises such as the low hums of jet engines are comparatively easier for headphones to identify and cancel out, as opposed to sudden, unpredictable sounds like people talking.

While the underlying physics remains constant, some companies excel more in active noise canceling than others. Armed with an understanding of how this process works, you can now choose the pair that best suits your preferences.