Noise Canceling Technology in Boruto

Ninja Technology in Boruto part 1


The world of Boruto and its parent manga Naruto is rather anachronistic at times.  This is a world where you can have radios, computers, dirigibles, and even trains being used alongside ninjas that fight using magic and weapons from the Warring States period of Japan.  Needless to say, trying to make heads or tails of it is a nightmare that I am not going to even begin to try.  However, I would like to highlight some of the more recent technology that we first saw used in Boruto.

noise canceling


The first device we see is arrayed around the edges of the arena and prevents Sarada, Boruto, and Mitsuki from hearing what the other is saying, let alone anything else.  In an extremely rare occurrence for any Shounen manga, Boruto tries to give a brief explanation as to how the technology works.



The question then becomes,what the heck is the device, how does it work, and is it actually possible?


Sound Waves

If you haven’t figured it out yet, the device in Boruto is an upscaled version of noise cancelling headphones and other noise cancelling devices.  These devices take advantage of the properties of waves.  The sounds that we hear are technically mechanical waves that are traveling through air, much like the waves we see in the ocean, except we hear the waves instead of seeing them.


The amplitude or height, of a sound wave determines how loud a particular sound is.  The higher the amplitude, the louder the sound.  Waves can travel at different speeds, but sound travels at 343 meters per second, or 767 mph at room temperature.  Yes, I know that the speed of sound in air will vary based on temperature, pressure, and humidity, but that’s a bit beyond what I am talking about today, and will have no impact on noise cancellation.  Since the speed of sound doesn’t change, the frequency or the number of times the wave repeats in a second is determined by the wavelength, or distance between the waves.  As the wavelength and frequency change we hear it as a change in pitch, with high pitch sounds having a higher frequency and short wavelength, and low pitch sounds having a lower frequency and longer wavelength.



Mitsuki states that the device is operating on a principle that is the opposite of resonance- so what is resonance?  The specific term Mitsuki mentions is acoustic resonance, which stands for constructive interference.  What both terms are referring to is how two different sound waves will interact when they come into contact with each other.  If two waves match up perfectly (in phase) they will be added together making a wave with an amplitude that is the sum of the previous two waves as seen below.


The opposite of constructive interference, or resonance, is called destructive interference, and this occurs when the two sound waves are the exact opposite of each other, or out of phase.  When two waves are out of phase the bottom of one wave (trough) matches up with the top (crest) of the other wave.  The result of these two waves interacting with each other is a cancellation of both waves.


Noise Canceling Headphones

Noise canceling headphones use destructive interference to cancel the incoming sound before it reaches the user.  A microphone detects the incoming sound and sends it to a control unit that determines the correct type of sound to emit from an attached speaker.  The emitted sound then cancels out the incoming sound.

noise canceling


The headphones are great, but while they do cancel out incoming sound, they are not perfect.  The headphones are better at canceling out constant lower frequency sound, like a motor running.  The system has a harder time canceling out higher frequency sounds and sounds that fluctuate, as the system needs to hear the sound before it can cancel it.  If the sound is constantly changing, the system would always be one step behind.  The headphones can also emit a hissing sound, which is the sound canceling wave.


Room Based Noise Canceling Systems

While there are a number of noise canceling systems that can be used in a room or even outdoors on the market today, I was not able to find a lot of solid information on them outside of the individual product pages.  The way the devices work is identical to noise canceling headphones, with similar drawbacks.  At best, most of the devices do not completely remove unwanted sounds, but drastically reduce them.


Other Noise Canceling Systems

I did find one more interesting device that, while not noise canceling, falls into the same realm.  The device is basically a sound gun, which records the incoming sound and then plays it back a fraction of a second later and it is meant to disrupt conversations in areas that are meant to be quiet spaces.  So it will not cancel out the people speaking, but it would make you pause for a second as you hear the words you just said played back to you.  It’s like hearing yourself through the other end of a skype conversation, a rather common and annoying occurrence when you are calling home from Mongolia.


The Device in Boruto

As stated by Mitsuki, the noise canceling device in Boruto does operate on the principle opposite of constructive resonance.  I wonder if there was a mistake in the writing or in the translation, because it would make more sense to say it operates on destructive resonance.  I do realize that there is no easy way in a few words to explain the scientific principle that allows the device to work, and this is a Shounen manga.  So, I will give Boruto props for actually giving a logical explanation as to how a device works.


As to the noise canceling device itself, Ukyō Kodachi was most likely inspired by noise canceling headphones and other noise canceling devices.  The problem is that any noise canceling device, real or otherwise, cannot completely cancel out the sound in a large room and/or something as complicated as people speaking.  This is due to the wider range of pitches and volumes being created.  There is also the delay that would occur, as speech is made of constantly changing sounds and the machine would always be a step behind.  Thus, I have to call the machine busted.


Now if the machine reduced ambient noise I would call it confirmed, due to existence of real world devices that can do the same thing.


A Possible Future Idea

Now if you asked me to come up with a sound-based noise-canceling technology for the Boruto manga, I would have recommended something similar to the real-world noise disruption device that I mentioned earlier.  While it would not cancel out the sound, it would be very effective at disrupting enemies from shouting their techniques and using their ninja skills. It’s also something that could be directed at individuals and not targeting everyone around you.