This is the first part in a multi-part blog in which we hope to answer some of your questions about Active Noise Cancellation (ANC) – what it is, how does it work, why do we want it, and why it is actually really hard to do!
To understand ANC, we must first grasp the basics. Sound is a variation of pressure in the air or other materials. Microphones capture these pressure fluctuations and convert them into electrical signals, allowing us to visualize and record sound. On the other hand, speakers receive electrical signals and transform them into time-varying pressures, which produce audible sound in the air.
The key to ANC lies within its name, with a focus on the last word, “Cancellation.” The concept is to eliminate unwanted sounds or pressure before it reaches your eardrums. This is achieved by measuring the incoming sound with a microphone, inverting the signal (flipping it 180 degrees in phase), and playing it back at your ear through a speaker. When the generated pressure from the speaker is precisely opposite to the noise pressure, the ear receives no sound – mitigating the noise.
In the ANC world, this actively generated sound is called the anti-noise, and it is produced in real time by the ANC device and a speaker that is mounted next to your ear. Sound travels at 340 m/s (1100 fps), so the speaker-generated anti-noise sound must be timed to arrive at your ear at precisely the same moment in time that the noise arrives. For a picture of what this process looks like, see the figure below:
Seems easy? While the above figure may make ANC seem simple, the reality is far more complex. The sounds that ANC seek to cancel often encompass a wide range of frequency content, and the amplitude and phases of the various sine waves comprising the signal are constantly changing. Additionally, the challenge lies in canceling only the unwanted noise while still allowing you to hear desired sounds, like music.
We encourage you to stick around for our upcoming posts, in which we will get into some more detail of Active Noise Cancellation. And we hope to give you a deeper understanding of this remarkable technology and its importance in building a better riding future.