How Does Noise Cancellation Technology Work?

The noise of an airplane, the constant murmur of an office, the distractions of working from home, and the sound of the subway: any of these can be enough to ruin a listening session. Active noise cancellation, known as ANC (Active Noise Cancelling), reduces them using the principles of physics. Understanding how it works helps you determine what type of ANC you need depending on how you use your headphones.

Even silence follows the laws of physics

Every sound is a wave that travels through the air. When two identical waves meet in opposite phases — meaning the peaks of one align with the troughs of the other — they cancel each other out. The result is zero. Silence. It is the same logic as adding +1 and –1: the result is zero.

ANC applies this principle in real time. Headphones capture the surrounding noise, generate an exactly opposite wave, and play it alongside the music. Your ears perceive the audio content without the background noise. This process repeats thousands of times per second, continuously adjusting to the sound reaching the microphone.

Noise cancellation is not 100% perfect, and no ANC system can guarantee that, but modern models can reduce low- and mid-frequency noise by as much as 25–30 dB. Those are precisely the frequencies where some of the most disruptive sounds are concentrated: engines, ventilation systems, and traffic.

The components that make active noise cancellation (ANC) possible

Three elements work together to make the process possible:

• Microphones. They capture surrounding noise before it reaches your ear, inside the headphone, or at both points at once, depending on the design.
• ANC processor. It analyzes the captured sound wave and calculates its inverse in fractions of a millisecond.
• Speakers. They reproduce the inverse wave together with the audio signal so that both reach your ear at the same time.

The speed of this cycle is what determines how effective the system is. The faster the processor analyzes the sound and the more accurately it generates the inverse wave, the better the cancellation.

Three types of noise cancellation

Not all ANC systems work in the same way. The difference lies in where the microphones are positioned and how the system responds to the environment.

Feedforward: anticipating the noise

The microphone is positioned on the outside of the headphone. It captures noise before it enters the earcup, allowing the system to generate the inverse wave in advance. It reacts quickly and is effective against constant, predictable sounds such as an airplane engine. Its limitation is that, because the microphone is exposed, it is more sensitive to wind.

Feedback: correcting what reaches your ear

The microphone is located inside the earcup, close to your ear. It measures the sound that actually reaches the eardrum and corrects in real time whatever has not already been canceled. It is less sensitive to wind, but reacts with a slight delay because it acts after the noise has already entered the earcup.

Hybrid ANC: the combination used by the best headphones

Hybrid ANC combines both microphones: an external microphone that anticipates the noise and an internal microphone that corrects whatever remains. The result is more complete and precise cancellation than either system can achieve on its own. It is the standard in premium headphones, including the MOMENTUM 4 Wireless and the ACCENTUM models in our range.

Adaptive ANC: cancellation that adjusts automatically

Adaptive ANC adds another layer of intelligence to hybrid active noise cancellation (ANC): the system analyzes the level of surrounding noise and automatically adjusts the intensity of the cancellation. In a quiet coffee shop, it calibrates itself differently than it would on the subway or during a flight. No manual intervention is required; the headphones decide how much cancellation to apply based on what they detect.

This is the feature that distinguishes the ACCENTUM Plus Wireless from the standard ACCENTUM Wireless.

ANC vs. passive isolation: they are not the same thing

Headphones reduce noise in two different ways, and it is worth understanding how they differ.

Passive isolation. This depends on the physical seal: the ear pads, the fit, and the material surrounding the ear. Because it does not rely on electronic components, it mainly reduces higher-frequency sounds, such as voices and high-pitched background noise. It works whether or not the headphones have battery power.

Active noise cancellation (ANC). This targets low- and mid-frequency sounds, precisely the frequencies that passive isolation is less effective at reducing. Engines, ventilation systems, and traffic are where ANC performs best. It requires power to operate.

Closed-back headphones in our range combine both layers. The seal created by the ear pads reduces high frequencies, while active noise cancellation (ANC) handles bass and midrange noise. The listening experience is the result of both mechanisms working together.

Transparency mode: when you need to hear what is happening around you

Transparency mode is the natural counterpart to ANC. It uses the external microphones to let surrounding sound in in a controlled way, without requiring you to remove your headphones.

It is useful in specific situations: having a short conversation, hearing boarding announcements at an airport, or crossing a busy street. Switching between ANC and transparency mode can be done with a single touch, without interrupting playback.

It is also an important feature if you exercise outdoors. In our guide to headphones for working out, we explain which models combine noise cancellation and environmental awareness depending on your routine.

The MOMENTUM 4 Wireless and ACCENTUM Plus Wireless both include this feature, with an adjustable transparency level through the Smart Control app.

How we have implemented ANC across our range

Designing ANC is only part of the work. The real challenge is ensuring that noise cancellation does not alter the headphone's sound signature: reducing noise without suppressing the music or introducing unwanted audio artifacts. It follows the same principle that defines high fidelity in headphones: reproducing audio as it was recorded.

This is how ANC is implemented across the main models in our range:

MOMENTUM 4 Wireless. Hybrid and adaptive active noise cancellation (ANC). The system automatically adjusts its intensity depending on the environment and can be extensively configured through the Smart Control app, including cancellation level, sensitivity, and mode preferences. It is the most complete implementation in our over-ear headphone range. See the differences between in-ear and over-ear headphones.

ACCENTUM Plus Wireless. Adaptive hybrid active noise cancellation (ANC) and transparency mode. The system automatically calibrates cancellation depending on the environment, following the same logic as the MOMENTUM 4 but at a more accessible price point. For people who move through several different environments during the day, it is an option that does not require constant manual adjustment.

ACCENTUM Wireless. Hybrid ANC with an on/off mode. There is no automatic adaptation: you decide when to activate it. It works particularly well in stable environments with constant background noise and offers a strong price-to-performance ratio within its segment.

If you want to understand the specific differences between the ACCENTUM models, the article ACCENTUM Wireless and ACCENTUM Plus Wireless: same family, different experience explains, feature by feature, what changes from one model to the other.

Active noise cancellation (ANC) is only one of the factors to consider. In our guide to choosing Bluetooth headphones, we cover the six that matter most.

Comparison table of ANC types

Frequently asked questions

How does noise cancellation work in headphones?

ANC headphones use microphones to capture external noise, a processor to generate an inverse sound wave, and the speakers to reproduce that wave together with the music. When the two waves combine, they cancel each other out and your ears perceive the audio with less background noise. The process repeats thousands of times per second.

What is the difference between hybrid ANC and adaptive ANC?

Hybrid active noise cancellation (ANC) combines external and internal microphones to provide more precise cancellation than either system can achieve on its own. Adaptive ANC goes one step further: it automatically adjusts the intensity of the cancellation according to the level of surrounding noise, without requiring you to configure anything manually.

Does noise cancellation affect sound quality?

In well-designed headphones, active noise cancellation (ANC) is calibrated so that it does not alter the sound signature. In the MOMENTUM 4 Wireless, for example, music remains faithful to the Sennheiser sound signature even when ANC is active. In less carefully engineered designs, slight coloration or residual noise may occur.

Does ANC work equally well with every type of noise?

No. ANC works best with constant low- and mid-frequency noise, such as engines, fans, and traffic. Its effectiveness decreases with high-frequency sounds or rapidly changing noises such as voices or background music. That is where the passive isolation provided by the headphones becomes more important.