Noise Cancellation: What is it and what does it do?
Passive or Active, noise-cancelling, find out which one is best for you.
(Updated on: October 30, 2021)
There are two kinds of noise-cancelling: active and passive. Some headphones have passive and active noise-cancelling functionality, while some only have passive noise cancellation/isolation. Each of these types of noise-cancelling block ambient noise differently.
- How does Sound travel and What are Sound Waves?
- Headphones with Active Noise Cancellation
- Difference between Active Noise-Cancelling and Passive Noise-Isolating headphones
- Passive or Active noise-cancelling: Which one’s for you?
- Noise-Cancelling technology: Is it safe to use?
How does Sound travel and What are Sound Waves?
The sounds that you hear are simply particles vibrating over a medium like air, water, etc. And the pattern that these sound vibrations travel in looks like a wave. Hence the term: sound wave.
Here’s a video demonstrating how sound travels through different mediums:
Sound travels faster through solid matter and liquids than it does through air. The speed of sound over the air is 343 m/s (meters per second).
It is easier to hear softer sounds like that of a pin dropping or a door opening, in a quiet room. But you barely notice these sounds when in a noisy environment. This is because louder sounds override softer sounds. We all understand this. As a result, when answering a call, we look for a quiet place so that we can hear the person’s voice.
Depending on the intensity of such vibrations, sound can travel vast distances and through multiple mediums, all in a matter of seconds. And as it travels in every direction from its source, it loses some of its power. This is why it sounds more powerful at the source and fainter as you get away from it.
Blocking out Sound Waves
Sound waves reflect off of all surfaces, however, certain materials like cloth, foam, etc. are capable of absorbing some of the sounds and minimizing the sound that is reflected. This makes them ideal for noise isolation as it blocks sound.
This is why foam is used as a sound-absorbant in most home or professional studios as it helps create high-quality acoustics. On the contrary, hard surfaces like metal or concrete reflect most of the sound waves, thus producing an echo effect.
Sound Waves and the Human Ear
As we mentioned earlier, sound waves are just vibrations created by drivers travelling through mediums like air. And when these air vibrations reach your ears, it causes your eardrums to vibrate.
From here, the vibrations travel to the Cochlea (a part of the inner ear). The brain then receives these vibrations as electrical signals that can be processed and understood as sound.
Here’s a video demonstration of this process:
Frequency is the measurement used to determine how many sounds hit the human ear per second. And frequency is measured in hertz (Hz) and is set as one cycle per second.
An increase in frequency means more sound waves are hitting the ear. And an increase in volume means a stronger vibration.
We (human beings) are capable of hearing sounds that range from 20 – 20,000 Hz. This range fluctuates as we age. Our hearing may also be susceptible to damage due to several other reasons. That is why it is important to take the necessary safety precautions to prevent unnecessary damage.
Noise and its Negative Effects
So at what point does sound turn into noise? The answer is when it starts to irritate and potentially harm you.
Constant noise exposure can cause irreversible harm to your health especially if not treated. This may in turn affect your personal and work life. Some of the negative effects of excessive noise exposure are as follows:
Hearing impairment – The unit used to measure the intensity or loudness of sound is Decibel (dB). The World Health Organization (WHO) recommends keeping the noise level below 70 dBA to avoid any hearing loss caused by loud environmental noises.
Difficulty communicating – Have you ever noticed how it is harder to talk to someone in a noisy environment like a rave or a party compared to a quiet setting? Extremely loud noises can not only harm your hearing but also your speaking abilities. And this can be pretty annoying. Being unable to speak and understand each other may cause miscommunication and affect productivity.
Psychological distress – High noise levels can worsen our mood by increasing our stress levels. The intensity of the sound could cause physiological as well as psychological excitation which might make us seem irritated and annoyed.
Sleeping disorders – Our body has a fight or flight response that can be triggered by extreme noise levels. This, as a result, can cause our body to react unnaturally. Thereby making us feel anxious and stressed which could lead to insomnia.
Cardiovascular diseases – While this is an extreme case, a combination of the reasons mentioned could potentially lead to cardiovascular problems. So it is best to stay safe by keeping ourselves within the noise exposure limits that our body is capable of handling.
What are the Headphones with Passive Noise Cancellation/Isolation?
Passive noise cancellation or more accurately, passive noise isolation is the proper term that should be used to describe this phenomenon. This is because the actual cancelling of noise is done using circuits and electrical signals which is used in the active noise cancellation process.
Either way, calling it passive noise cancellation or isolation is unlikely to cause any confusion. Physics is what allows passive noise isolation to work the way it does. Since we like talking about headphones and speakers, the air is the medium that sound uses to travel.
By stopping the air outside the earcups from coming inside, the sound inside remains undisturbed. And as we said earlier, certain materials are better are doing this like foam. That is why the material or padding of earcups is so important. This creates a good seal by reducing sound leakage which promotes noise isolation.
While there is still some leakage, it is negligible. Over-ear or circumaural headphones tend to be the best at noise isolation. Within these, closed-back headphones achieve a much better seal as opposed to open-back headphones and for obvious design reasons.
Why should you consider buying Passive over Active noise-cancelling headphones?
Here are some reasons why you might consider passive noise cancellation (noise isolation) headphones:
Price – Passive noise isolation is the cheaper technology and as such, the price of headphones are comparatively lower. ANC technology requires additional electrical parts which costs more. That said, you can find some budget-friendly active noise-cancelling headphones.
Don’t consume battery life – As no electrical parts are required for noise isolation, there is no additional power consumed. This allows you to keep using your Bluetooth battery-powered device for much longer. It also reduces battery degeneration.
Sound quality stays unchanged – Active noise-cancelling technology/headphones need to process the sound before relaying it back to your ears. This process affects the sound quality.
Passive noise-isolating headphones are simple and intuitive to use which makes them appealing to the majority of people. It delivers good sound performance while needing very little maintenance.
Headphones with Active Noise Cancellation
Active noise cancellation (ANC) technology uses small microphones to listen to the noise around us. This noise is then filtered from your music using the noise-cancelling system.
You should get a pair of ANC headphones if you live in a noisy neighbourhood and need to sleep peacefully. Passive noise-isolating headphones can reduce the loudness of mids and highs by about 15dB to 30dB.
While ANC headphones can reduce the loudness by 20dB to 45dB of midrange and low-end frequencies (this is most of the ambient noise resides in). This also reduces the need to increase the volume of your music, thus protecting your ears.
Types of Active Noise Cancellation
As we now know the basic principles behind ANC, it’s time to talk about the different types and parameters for implementing it.
Feedforward ANC – For this ANC setup, a feedback microphone is attached to the outside of the earcup. The headphones’ speakers provide anti-noise signals in response to incoming noise detected by the ANC system. Being outside, the microphone can pick up ambient sound more quickly. Still, being unable to communicate with the ANC chip’s signal, limits the resulting range of counter frequencies.
Feedback ANC – A feedback microphone is positioned inside the earcup, just ahead of the speaker. This allows the mic to hear what the listener hears. Consequently, its ability to adapt to variations in soundwaves is greatly enhanced. However, it is unable to block noise within the range of 1-2 kHz, which puts it behind feedforward ANC.
Hybrid ANC – This ANC type combines the advantages of both feedforward and feedback ANC. Two mics (one outside and one inside) allow the ANC process to adapt and respond quicker and more precisely. Additionally, it covers a wider range of frequencies. The catch is that it costs twice as much as the previous two ANC types.
Adaptive ANC – Qualcomm’s Adaptive ANC is the newest kid in town. It works by listening to the noises around you and adapting to them (similar to Hybrid ANC). However, it claims to provide an extended battery life with better sound quality. It also has a leak-through feature that allows some ambient noise to enter by adapting the level of noise cancelling to your environment.
Why should you consider buying Active over Passive noise-isolating headphones? Are they worth it?
Active noise-cancelling or ANC technology is a lot more effective at blocking or filtering out unnecessary noises. This is their biggest advantage over passive noise isolation or PNC headphones.
If you have ever travelled by plane or any other means, then you must be familiar with the rumbling noises of engines and other loud sounds. Bearing with them for long hours might be detrimental to your hearing and mental health. But an Active noise-cancelling headphone will block all of those annoying sounds, making you feel much calmer, almost instantly.
This technology costs more to manufacture as it is complicated, boosting the price quite a bit. It will also use up battery power to run and can get some getting used to. That said, it does give people the ability to mute the world at will. Extremely loud noises can stress you out and compromise your health, this is why ANC headphones are a good investment.
Difference between Active Noise-Cancelling and Passive Noise-Isolating headphones
Most headphones buyers think that noise cancelling and noise isolating headphones are the same. But if you have read this far then you know that this isn’t the case. There are several differences between them, knowing these differences will help you choose the right headphone for you.
Passive noise-isolating headphones work by understanding how sound interacts with objects or matter. And certain materials like foam or cloth have sound-absorbing properties that reduce noise.
On the other hand, active noise-cancelling headphones employ technology that is specifically designed to understand and eliminate sounds that aren’t part of the audio that you’re listening to.
Among these two, active noise-cancelling is more effective at noise reduction. But the fit of the headphones, as well as the materials used for padding, affect the noise reduction efficacy.
Don’t expect 100% of ambient noise reduction from noise isolation or noise cancellation headphones. Even premium noise-cancelling headphones are capable of blocking about 95% of ambient noise.
Manufacturers of noise-isolating headphones don’t need to spend money on electronics that noise-cancelling headphones require. This draws their focus towards the design language and materials that could improve the build as well as the sound quality of the headphones.
Now, ANC technology requires processing the sound of the audio that you’re consuming and the ambient noise to determine which sounds to “cancel”. This does affect the sound quality a little. One way to spot the difference is to listen to the sound with the ANC turned off and then once when it’s turned on.
Some ANC headphones like the Bose NC700, Sony WH-1000XM4, and the Shure Aonic 50 can maintain the sound quality with almost no change in the mix.
Generally, ANC headphones are costlier than PNC (passive noise-isolating) headphones. For the obvious reason that ANC technology requires more parts and inventment to manufacture. Quality control is very important for such premium headphones.
Depending on you how much you’re willing to spend, you can get a passive or an active noise-cancelling headphone. You will find cheap ANC headphones, but the actual ANC performance of such low-end devices tends to be mediocre or above-average at best, especially compared to premium models.
As time passes, ANC technology will become more and more affordable. That is when we’ll see ANC headphones at competitive, low prices. Note that the price may be lower or higher depending on the brand, model, etc., regardless of its noise-cancelling type.
Safety and Comfort
The effectiveness of noise isolation greatly depends on the fit and seal of the headphones. If the fit can’t be too tight or too loose, it has to be just right or it will affect breathability, trapping the heat and causing the ears to sweat. If the fit is too tight, it may even cause pain. This is why noise-isolating headphones usually provide a better fit compared to ANC headphones. Premium ANC models are an exception.
When it comes to safety, it is best not to use ANC headphones in situations when it is crucial that you stay aware of your surroundings e.g. while running or cycling, etc. In situations like these, noise-isolating headphones are favourable as they don’t block out all the sound. Or you could simply turn the ANC off if your headphones let you do that.
Passive noise-isolating headphones consume less power (or no power if you have a wired headset) as they don’t have any extra electronic parts that could drain battery life.
On the contrary, active noise-cancelling headphones need to be battery-powered to function properly. Even with a substantial battery backup, you will have to charge it once in a while to keep using the ANC feature.
Passive or Active noise-cancelling: Which one’s for you?
Deciding on which type of headphones you should get depends on what activities you’ll be using them for. Passive noise-isolating headphones are favourable in some situations and active noise-cancelling headphones in others.
Athletes – During workouts, people like to stay focused and not get distracted, this is where ANC headphones are ideal. You can listen to your music and easily get in “the zone”. Because let’s face it, the gym’s music taste can be questionable, you may or may not like it.
Noisy workplaces and environments – There are all kinds of sounds that make up the ambience of office space. And we bet that you don’t want to hear any of it. ANC headphones will completely mute those sounds for you. But passive noise-isolating headphones are better suited in this environment.
This is because you may want to hear certain sounds like when someone is calling out to you and block out the rest. produces all sorts of noise especially those with open floor plans.
Travellers and Commuters – Travelling by trains or any other means expose you to a lot of noise, unsurprisingly. But what if it gets to the point when you can’t even peacefully appreciate the visual appeal of a place. Maybe you’re commuting to and from work and you’re greeted with engine noise, people chatting, etc.
Dr Amar Bose was in a similar situation, and that’s what lead him to create the first noise-cancelling headphones. This is why a pair of active noise-cancelling headphones are perfect for handling the noise found in such environments.
Stay focused while learning – No study, no work, no money…you see where this is going? Focus, that’s what we need when we attempt to learn something. And active noise-cancelling headphones can and will help you do just that, stay focused. But let’s not forget how no play and all work made Tom a very dull boy.
ANC headphones mute your surroundings and let you focus on your gameplay. So even while gaming, these work wonderfully.
Noise-Cancelling technology: Is it safe to use?
Yes, headphones fitted with noise-cancelling technology are safe.
In fact, ANC technology was invented to provide hearing protection for pilots, to shield them from the loud noises of the plane’s engine. This is what makes them so great at reducing noise and preventing potential hearing loss and stress.
Most ambient noise like an engine’s rumble or an AC, fall in the low-end frequency range. And noise-cancelling headphones are apt at eliminating that. Reducing these sounds means that we don’t have to increase the headphones’ volume to compensate. Which could result in ear damage. This is especially valuable for adults and children with sensitive hearing.
Some premium ANC headphones also come with features like a volume limiter (for limiting children’s exposure to loud noise) and can also block mid-range frequencies like voices. People also wonder if Bluetooth technology is safe. And it is.
Other safety concerns with ANC headphones
Pressure on the ears – One of the most common criticisms that people who use noise-cancelling headphones involve experiencing pain in and around the ear.
They particularly complain about ear pressure (similar to the pressure you feel when an aeroplane takes off). And we feel that way due to a change in barometric pressure. So people can handle it and others can’t. And noise-isolating headphones are a better option for the ones that can’t.
Tinnitus – A problem that affects kids and adults equally. If you experience a constant buzzing or ringing sound in the ears then this condition is called tinnitus. This sound becomes more severe with the lack of ambient noise. Several things can trigger this reaction, and some people have reported this condition due to using noise-cancelling headphones. Though, there isn’t any scientific relationship between those two.
A product called Calmer by Flare Audio could benefit people that regularly have sensitive hearing or have to deal with noise-induced stress or tinnitus. It is a simple, silicone device with no electrical parts, that goes inside the ear to reduce the distorted midrange frequencies.
Reduces awareness – Sometimes it is crucial to hear sounds especially if it means keeping yourself safe. Research has found that wearing headphones in busy surroundings put you at risk of an accident.
Most people reach for their headphones when they leave the house to run an errand or for a run. And we understand the temptation of having headphones on and not playing music. But it’s important to not give in, and make sure that nothing in our environment could harm us. Doing so will significantly decrease our chances of getting into an accident.
A tech company called Audio Analytic has created an audio recognition software named ai3™. It is designed to be installed into headphones and speakers. Its objective is to alert the listeners to specific sounds like that of a car horn, sirens, etc. Impressively, it also works alongside headphones with ANC technology.