Noise-cancelling headphones: The what, how and why

Imagine trying to enjoy your favourite music on a flight, only to have it drowned out by engine noise, conversations and crying babies. Turning up the volume might seem like the obvious solution, but listening at high levels for extended periods can damage your hearing. And instead of helping you relax, all that background noise can quickly become a source of stress.

Fortunately, there are headphones designed to keep unwanted sounds at bay. But how do they actually work? Let’s take a closer look at the two main approaches: passive noise isolation and active noise cancellation (ANC), and what sets them apart.

Passive Noise Isolation: How Headphones Block Out Sound

Passive noise isolation works by physically blocking sound waves from reaching your ears. Rather than actively cancelling out noise, headphones create a barrier between your ears and the surrounding environment. In-ear headphones do this by forming a seal inside the ear canal, while over-ear and on-ear headphones use padded ear cups to cover or cushion the ears, reducing the amount of external sound that gets through.

The effectiveness of this approach depends largely on the design and fit of the headphones. In-ear models can provide particularly good noise isolation, but only if they fit snugly inside the ear canal. That’s why they usually come with several sizes of ear tips, allowing you to find the best fit. Some high-end manufacturers even offer custom-moulded ear tips tailored to the shape of your ear canal for an even more precise seal.

Over-ear headphones can also block out a considerable amount of background noise, particularly lower-frequency sounds. However, no passive noise-isolation design can eliminate all external sounds. In fact, virtually all headphones provide some degree of passive noise isolation, although the amount varies considerably depending on their construction and fit.

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Active Noise Cancellation: Using Sound to Fight Sound

Active noise-cancelling headphones (ANC headphones) take a different approach to reducing unwanted sounds. Rather than physically blocking them out, they use sound waves to counteract incoming noise. To understand how this works, it helps to know a little about the nature of sound.

Sound travels through the air as vibrations, creating alternating changes in air pressure. These are known as compressions (areas of higher pressure) and rarefactions (areas of lower pressure). When represented graphically, sound waves are often depicted as sine waves, with peaks representing compressions and troughs representing rarefactions.

When two sound waves with the same frequency and amplitude meet, their interaction depends on how they align. If their peaks and troughs coincide, they reinforce each other, making the resulting sound louder. If they are exactly opposite, with the peaks of one wave aligning with the troughs of the other, they can cancel each other out. This phenomenon is known as destructive interference.

ANC headphones use this principle to reduce ambient noise. Built-in microphones pick up sounds from the surrounding environment, and the headphones’ electronics analyse them to generate an opposing sound wave, often called anti-noise. The headphone drivers then reproduce both your audio and this anti-noise signal. When the two sound waves meet, they partially or, under ideal conditions, completely cancel each other out.

However, noise cancellation isn’t perfect. The technology is generally most effective against continuous, low-frequency sounds, such as the rumble of aircraft engines or the hum of air conditioning. Sudden or higher-frequency sounds, such as a crying baby or nearby conversations, are more difficult to cancel out, although their volume can still be reduced. The effectiveness also varies between headphone models, manufacturers and price points.

Don’t forget: ANC stands for Active Noise Cancellation

In order to process ambient sound and produce a corresponding “anti-sound,“ noise-cancelling headphones include small computers that require batteries – either rechargeable or disposable – to run. When these run out, the headphones continue to function as headphones, but their noise-cancelling function ceases to operate. In addition to power demands, the ANC function requires a degree of space. With on- and over-ear headphones, this is in the ear piece itself; with in-ear headphones, the processing unit is usually located in the cable and looks similar to a larger in-line remote.

Noise Cancelling vs Noise Isolation: Which Should You Choose?

At first glance, active noise-cancelling headphones might seem like the obvious choice. After all, they use built-in electronics to actively counteract unwanted sounds, rather than simply relying on physical barriers. But it’s not quite that straightforward. ANC technology has its limitations and doesn’t block all frequencies equally well, with higher-frequency sounds often remaining more noticeable. As a result, a good pair of noise-isolating headphones can deliver a surprisingly similar experience – often at a lower price and without the need to charge or replace a battery.

This was put to the test by hi-fi journalist Steve Guttenberg in an article comparing noise-cancelling and noise-isolating headphonesOpens in new tab. He tried both types on the New York City subway, where the screeching of trains as they round corners is accompanied by plenty of rattling and clattering. The experience gave him a newfound appreciation for noise-cancelling headphones, despite his initial skepticism towards the technology. However, he also pointed out that most ANC headphones don’t offer quite the same sound quality as conventional hi-fi headphones at a similar price. His takeaway? Think about where you primarily listen to music before deciding which type of headphones is right for you.

Noise-Cancelling Headphones from Teufel

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▶ AIRY TWS 2Opens in new tab: Wherever you are, sometimes you just want to enjoy your music without distractions. The AIRY TWS 2 are Teufel’s innovative in-ear headphones with active noise cancellationOpens in new tab (ANC), giving you a more immersive listening experience. Need to hear what’s happening around you? Simply switch to Transparency Mode.

▶ REAL BLUE PROOpens in new tab: Tune out the world around you and enjoy your music without distractions from traffic or busy crowds. These premium hybrid ANC headphonesOpens in new tab feature lightweight Linear HD drivers and support High Resolution Audio. With over 44 hours of battery life with ANC enabled, they’re also ready for long-haul flights.

▶ AIRY OPEN TWSOpens in new tab: Stay aware of your surroundings while enjoying your music. Thanks to their open-ear design, these headphones let you hear ambient sounds, making them a great choice for wearing in traffic or other situations where awareness is important.

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Conclusion

• Noise-cancelling headphones use advanced technology to significantly reduce unwanted background noise.
• They’re particularly useful for frequent travellers, people working from home and anyone who regularly listens to music in noisy environments.
• Teufel offers a range of high-quality noise-cancelling headphones for different needs.
• Noise-isolating headphones are also an effective option. Without additional electronics, they’re often simpler to use and don’t require charging.
• Conventional headphones without dedicated noise-reduction technology can be an excellent choice for home listening, particularly if you prioritise sound quality and value for money.