Active Noise Cancellation explained. Drawbacks, and how it differs from other forms of noise cancellation

We come across hundreds of tech jargon these days, and while most of them are merely gimmicks, there are a few, which actually add value to your gadgets, and make our lives more convenient. One such thing is active noise cancellation, which you will often find while purchasing headphones, earphones, TWS,  microphones, and different other audio devices of this generation. 

Audio devices with this technology are a little expensive, however, it has been far democratized, with brands having quality offerings at affordable rates. If you do not know what noise cancellation is, I will explain it on InkedFreedom today. Once you know what active noise cancellation or ANC is, you will not be misled while purchasing audio devices with noise cancellation technology.

But, before explaining active noise cancellation technology, let’s first have a basic overview of what sound is, or better, how we perceive sound through our ears. 

How do we perceive sound waves?

When a body vibrates, it creates continuous synchronized expansion and compression of the medium around it, forming a wave with crests and troughs back to back. This wave propagates through a medium, which is the air, in our everyday lives and our ears perceive this vibration as sound or sound waves.

Active Noise cancellation explained

Following the above analogy, what if we could create a sound wave, which is the same, but is exactly opposite to a sound wave! To make it clearer, in the new opposite sound wave, the crests and troughs will be replaced by each other. So, the phased-out opposite sound wave cancels out the original wave leading to complete silence.

Here’s an illustration of what I said.

Now that you know how we perceive sound, and how to cancel out a sound with an exactly opposite sound through phase cancellation, it is the most basic form of active noise cancellation. In the case of earphones with active noise cancellation technology, there are microphones that are intelligently placed at different parts of the earphones or headphones to capture the ambient noise.

The combined noise that the listener is supposed to hear, is then fed to an active noise cancellation chip, which uses complex digital signal processing algorithms to analyze this noise, and create a phased-out sound, which is eventually played through the earphones along with the actual sound that is supposed to be played.

Here is another illustration of the practical world scenario, the sounds that we hear, and how noise is canceled.

So, what we hear is the original sound that can be a song, podcast, or anything of our choice, the external noise, and its phased-out version. Hence, we can just hear the original sound, as the external noise is getting canceled out.

How effective noise cancellation is?

Well, you might already have an idea by now that active noise cancellation requires additional algorithms to function. How smart the algorithm is, among other aspects, has a significant impact on the performance.

Microphone placements matter

The microphones play an integral part in how effectively active noise cancellation works. Besides the quality of the microphones that do the primary task of capturing ambient noise, these are intelligently placed to have a better understanding of the noise that reaches the ears of the listener. 

In most headphones, the microphones are placed within the ear cups close to the ears to closely monitor the noise and offer optimum noise cancellation. However, if that is not possible, especially in the case of earbuds and earphones, they are kept outside, but as close as possible to the ears. In some premium models, the microphones are kept both inside and outside to deliver the best possible experience.

Check the cancellation levels

Based on the level of active noise cancellation, you might still hear some ambient noise that is louder than your earphones can cancel. Say for example, if your earphones have noise-canceling ability up to 30 dB, any external noise louder than 30 dB will not be canceled, and hence will reach your ears.

However, it doesn’t mean a baby crying, which is far louder than 30 dB will be audible as it is. Your earphones will still try to cancel it, and because of the seal of the earphones within the ears, you will not hear it as loud as you would, without the earphones and ANC in place.

Don’t underestimate passive noise cancellation too

Even earphones with active noise cancellation require good noise isolation to deliver the best performance. That is the reason why you will often find over-the-ear headphones with ANC offer better performance than a pair of earphones, even if they are evenly priced.

How is active noise cancellation different from passive noise cancellation?

Now that you know what active noise cancellation is, you might want to know why the word “ACTIVE” is used. In all the earphones that we use, the physical shape and construction of the earphones will block some ambient noise. The better the seal of the earphones within our ears, or the better they fit in our ears, the more will be the ambient noise that would be canceled. This form of noise cancellation is called passive noise cancellation, aka. noise isolation.

Passive noise cancellation or noise isolation is similar to holding the palm on the ears or covering the ear cavity in some other way, both of which block some external noise, however, some noise will still make its way to our eardrums. Passive noise cancellation or noise isolation don't involve any fancy physics, but can still be useful, if you are on a tight budget, and mostly enjoy audio indoors. 

Depending upon the build type of the earphones or headphones, passive noise cancellation can sometimes offer a better noise cancellation experience than earphones with active noise cancellation. Most cheap noise-canceling earphones offer the same level of noise cancellation as the passive noise cancellation experience of big over-the-ear headphones, simply because of the design, and the magic, passive noise cancellation does.

If you are getting some earphones, and the box reads, noise cancellation, it perhaps refers to passive noise cancellation. As ANC or active noise cancellation requires additional engineering, if, the manufacturer will certainly market it if the feature is live on the audio peripherals that you are buying

Drawbacks of active noise cancellation

Even though active noise cancellation is a great and fancy technology offering optimum audio experience, this amazing technology isn’t short of drawbacks.

Additional processing requires more power

Unlike other wired earphones that are capable of playing audio right from the 3.5 mm audio jack or the Type-C port, earphones with active noise cancellation require additional power to capture ambient noise, process it, and create its phased-out wave.

In the same way, Bluetooth earphones with active noise cancellation will require more power for all the extra processes. What you will end up with is shorter battery life. This might not be a big drawback, compared to the benefit, but if you enjoy music for longer hours, this will certainly impact you.

Heavy processing can impact the quality

With earphones having ANC or active noise cancellation enabled, you are listening to audio that has been processed in some way. If the processing isn’t that fine, especially with cheap earphones with ANC, the audio output might fail to impress you. Even if you are using a premium pair of earphones, it will still involve optimized processing that you might not realize, but a true audiophile can feel the difference.

Motion sickness can disgust your travel plans

Most people have the habit of using one earphone to enjoy music or attend calls. Though that is perfectly alright if you are somebody who suffers from motion sickness while traveling, using one earphone with ANC on can make you sick. Not just one, even if you are using the earphones in both ears, you can still feel sick, if you suffer from motion sickness.

Treat to the ears can turn life-threatening on the streets

Listening to your favorites while ignoring the outer world is total bliss, as long as you are indoors. The moment you step out, this can be life-threatening, and awkward too. As active noise cancellation makes everything silent, or at least close to that, you are unaware of a car or any other vehicle approaching, and this can cause severe accidents. In an office setup, with ANC on, you will hardly hear if a colleague calls you by name. However, that is exactly when transparency mode comes into play, which uses the same technology under the hood.

What is transparency mode?

Unlike the noise cancellation algorithm, where the ambient noise is canceled out, in transparency mode, the external or ambient sound is played through the earphones, as if no earphones are put in the ears.

While noise isolation or passive noise cancellation still offers some level of noise reduction; with transparency mode on, the endeavor is to keep the ambient noise reduction to the minimum levels and keep the listener aware of the surroundings. Some manufacturers might call this differently, like Samsung calls it Ambient Sound Mode, however, they all function in the same way, with minor modifications to the rudimentary algorithm.

But, you shouldn’t blindly walk through the middle of the road with transparency mode on, as it is not always accurate, just like ANC can’t make you feel complete silence. If you are listening to music at an extremely high volume, which isn’t good, even transparency mode will fail to keep you aware of the surroundings.

Similarly, in several places in India, a penalty can be imposed if you wear earphones while driving or crossing the road. If such a penalty is imposed on you, convincing the authorities about transparency mode is not going to bring the odds in your favor. So, if such laws are there, you should avoid using earphones, no matter how well the transparency mode is.

So, that’s all about active noise cancellation. Have any questions? Feel free to comment on the same below.