Noise-canceling headphones and earbuds are incredibly beneficial. If you’ve ever used a pair, you’ll appreciate their ability to provide a peaceful, noise-free listening experience, perfect for enjoying music, blocking out commuting noise, and even for working. If you’re considering investing in a set, you’re in for a great experience. However, it’s important to note that not all noise-canceling products are created equal. Many of these devices share some common audio technology.
One key feature found in several noise-canceling headphones and earbuds is called active noise cancellation (ANC). When discussing noise cancellation, you can think of ANC as the foundational technology. But how does this sophisticated circuitry and sound processing work? What do the technical terms really mean? Who are the leading brands in this space? We’re here to provide you with a straightforward introduction to ANC and its various audio applications.
What is active noise cancellation?
If you ever took an Introduction to Physics class in high school or college, you may remember a section that covered waves. Waves made of water, or light, or sound all share a few intrinsic properties. ANC technology takes advantage of one of these properties: Any wave can be effectively “canceled” if you create a second wave that is the exact opposite of the first wave — a process known as destructive interference.
So if you can create a set of headphones that can listen to the outside world and instantly create a set of sound waves that are the exact opposite of the sound waves it hears (a.k.a. anti-noise), then, in theory, you wouldn’t hear the external sounds at all — they would have been canceled before ever reaching your eardrum. That’s exactly what ANC does.
Bose, the company that developed the first commercial ANC headphones for pilots, and then the first ANC headphones for the general public, describes it like so:
With microphones inside and outside the earcups, Bose noise-canceling headphones continuously sense, measure, and send unwanted sounds to proprietary digital signal processing chips which compute a precise, equal, and opposite signal to react to changing noise in less than a fraction of a millisecond. The result is surrounding noise all but vanishes.
Not all ANC is created equal, however, which means that even though all ANC headphones and earbuds use this same principle, there can still be big differences between brands and models.
Active versus passive noise cancellation
As great as ANC can be, it’s worth noting that it’s not the only way to deal with noise. Passive noise cancellation (sometimes called passive noise isolation) takes a decidedly low-tech approach to the problem by creating a physical barrier between your eardrums and external sounds.
It’s usually accomplished by creating a tight seal around your ear (if it’s a set of headphones) or inside your ear canal if you’re using earbuds. Either way, the result is the same: You won’t hear a sound that can’t make it to your eardrums in the first place. When passive noise cancellation is done well, it can be so effective that you don’t feel the need for anything else.
It’s also worth noting that despite using different approaches, active and passive noise cancellation are actually complementary to one another. The more sound you can passively block, the better ANC technology can cancel the sounds that still make it through.
Think of it like paint: If you use a coat of primer on your walls, you’ll probably need fewer coats of paint to get the color and coverage you want, than if you simply applied the paint directly.
What’s the difference between ANC and ANR?
You may have seen the term Active Noise Reduction, or ANR, in addition to the more common ANC. In practice, there’s no difference between them. Each company uses its preferred label, but it’s the same feature.
Interestingly, Bose uses both terms, but in different circumstances. When Bose makes its own noise-canceling headphones, it calls them ANC, because Bose has been 100% responsible for how those headphones perform. But sometimes third-party companies will license Bose’s noise-canceling technology to create their own ANC headphones. Amazon did this when it introduced its first-generation Echo Buds. When that happens, those third parties use the term ANR to refer to Bose’s contribution, as a way of indicating that Bose wasn’t involved in every aspect of the headphones’ performance.
How do ANC headphones and earbuds work?
All ANC headphones and earbuds use microphones to detect external sounds. An onboard microprocessor then analyzes those sounds and feeds the required opposite sound waves to your ears via the headphone’s speakers. Amazingly, this can be done whether you’re playing music or not.
Some ANC models use “feedforward” microphones. These mics are placed on the outside of the headphones, where they’re able to pick up external sounds clearly and quickly. But feedforward ANC systems don’t know what happens to external sounds as they pass through the noise-isolating barrier of the earcups (or ear tips). This means that the anti-noise they produce may not be a perfect match for the noise that enters your ears.
Other ANC systems use “feedback” microphones, which sit inside the earcups of the headphones. They get the most accurate reading on the external sounds that have penetrated the headphones, so they should be able to create the most accurate anti-noise. But these systems aren’t as adept at canceling high-frequency sounds as feedforward mics. They also have to contend with any music you’re listening to. Being able to distinguish between the sound you want to hear (your music) and the sound you want to cancel can be tricky, and feedback systems run the risk of canceling out some of your music.
As you might expect, the best ANC systems use a hybrid of the feedforward and feedback models and use both internal and external microphones to combat noise. If you see a set of headphones that list “Hybrid ANC,” it uses this method.
Adaptive ANC
A relatively new term in the headphone space, Adaptive ANC can mean different things depending on the model of headphones and the technology being used.
Qualcomm’s Adaptive ANC technology, for instance, helps ANC circuitry respond in real-time to changes in the amount of external sound that makes its way inside the sealed area of the headphones. It’s an attempt to compensate for the fact that there are hundreds of different ear and head shapes, making it hard for any one model to fit all people perfectly.
Even if you get a great seal with a set of earbuds, as you walk, run, or even talk, the earbuds will naturally shift around inside your ear, causing that seal to change. Qualcomm’s Adaptive ANC responds to these changes.
Another form of Adaptive ANC relates to the algorithms used by the ANC circuitry. External sounds are constantly changing based on our environment. Indoors, we probably encounter lots of people speaking, while outdoors we could be faced with traffic sounds, and on an airplane, it’s mostly the white noise of a jet’s engines. Many companies offer smartphone apps that let you select the appropriate ANC mode based on your surroundings, but Adaptive ANC systems attempt to analyze those changing sounds and shift modes automatically so that you’ll always have an optimized noise-canceling experience.
What makes one set of ANC headphones better than another?
This is the million-dollar question. The honest answer is everything. ANC is much more than just external and internal microphones combined with some circuitry. It’s the number, placement, and kind of microphones used. It’s the quality of the electronics used to tie the components together. It’s the sophistication of the noise-canceling algorithms, and it’s the sensitivity of the drivers used to produce both sound and anti-noise.
Because ANC is so complex, buyers need to beware of manufacturer claims like the amount of noise canceled as expressed in decibels (dB). You may see a set of ANC headphones that claims to cancel -35dB of noise. But what does that mean? Unwanted sound isn’t just measured in loudness — it’s also composed of a spectrum of frequencies. If the ANC system reduces high-frequency sounds by -35dB, but hardly reduces low-frequency sounds at all, is that good or bad? If you’re trying to block out the sounds of the neighbor’s kids (or maybe your kids) shrieking while they play, it could be very helpful. But since most of us aren’t going to want to wear different headphones to block different noises, it’s probably not the right choice.
Our advice, you will not be surprised to hear, is to read reviews, both professional and buyer-based, to learn how your chosen model deals with a variety of situations.
What can I expect from a good set of ANC headphones?
Any ANC headphones or earbuds that are worth having should produce an immediate and very noticeable reduction in external noise. Most ANC headphones also have a transparency mode too, which is designed to let lots of noise in (so you can maintain awareness of hazards or have conversations without removing the cans). In an ideal world, transparency mode makes you feel like you aren’t wearing headphones at all.
When you turn transparency and ANC off, things should get much quieter, but you’ll still be fairly aware of outside sounds. Turning ANC on should substantially reduce those remaining sounds. In some cases, ANC can make a sound (like the droning of a fan) disappear completely, leaving you with an almost perfect sense of calm and quiet.
What are some signs of bad ANC headphones?
The first and most evident sign of ineffective Active Noise Cancelling (ANC) is the lack of noticeable sound dampening when the feature is activated. While this might seem like a straightforward observation, many users have experienced models where distinguishing when ANC is engaged feels nearly impossible. Ideally, engaging ANC should create a discernible reduction in ambient noise, allowing you to enjoy your music in peace. If this isn’t happening, it raises questions about the quality and effectiveness of the ANC technology being utilized.
Another significant issue arises when the ANC feature starts to compromise the audio quality of your music. It’s important to remember that the same speakers responsible for playing your favorite tracks are also tasked with generating the anti-noise signals meant to cancel out distractions. If the ANC system is overly aggressive, improperly tuned, or grappling with various deficiencies, you might notice a decline in sound quality when ANC is active. This could manifest as a loss of detail, muddied mid-tones, or a reduction in the overall clarity of your music, making your listening experience far from enjoyable.
Moreover, poorly engineered ANC circuitry can inadvertently introduce new types of noise, even as it attempts to counteract unwanted sound. A common complaint is the presence of a hissing sound that becomes noticeable during periods of silence or while playing lower-volume content. While listening to music can help mask this hiss, it can be particularly frustrating for those who use their headphones as a means of isolation, akin to earplugs. In those moments, the persistent, unwanted hiss can be incredibly annoying, detracting from the intended use of high-quality headphones and leading to disappointment among users seeking tranquility.
What about Environmental Noise Cancellation (ENC)?
When evaluating product descriptions for headphones or earbuds, it’s crucial to pay close attention to specific terminology that can significantly impact your listening and calling experience. Terms such as Environmental Noise Cancellation (ENC), Clear Voice Calling (CvC), and noise-canceling (noted without the “active” designation) are particularly important. These features refer to the technology embedded in microphone circuitry that actively minimizes the interference of background sounds when you engage in voice calls or record audio.
ENC is designed to enhance your calling experience by filtering out ambient noise, allowing your voice to be transmitted more clearly to the other party. This feature is especially beneficial in noisy environments, such as busy streets or crowded cafes, where background sounds can easily disrupt communication. Similarly, CvC works to optimize vocal clarity by reducing distracting sounds during calls, ensuring that your voice is front and center.
While these features are essential for anyone who intends to use their headphones for voice calls or audio recording, it’s important to note that they are not alternatives to active noise cancellation (ANC). ANC is a different technology aimed at reducing external sounds, providing a more immersive listening experience while enjoying music or other audio content. The ENC and CvC functionalities will not lessen the noise you experience while listening to music or wearing the headphones in silence. Instead, they focus solely on improving the clarity of your voice during conversations.
In summary, if you plan to use your headphones or earbuds primarily for phone calls or voice recording, seeking out models that highlight ENC and CvC capabilities will enhance your experience significantly. However, for those looking to block out ambient noise while listening to music, active noise cancellation features should be your primary focus.
