Noise cancellation in headsets: What is it, and how exactly does it work?
Noise cancellation is very much the tech expression of today – at least in the audio world. Every headphone producer s →
Active noise cancellation (ANC) has become a popular feature in music headsets. Many headsets now boast ANC, but not all of them are created equal. Let’s see why.
This is the second part of our look at why not all ANC headsets are alike. In the first part, I’ve talked about how active noise cancellation itself comes in a few different flavors: feedforward, feedback, and hybrid. The hybrid approach works best but costs the most.
But even going with the expensive hybrid ANC solution doesn’t guarantee that you’ll get the perfect ANC headset. Why? Because aside from the ANC technology itself, there’s also the matter of how the headset is designed.
When designing an ANC headset, engineers may be tempted to use digital signal processing (DSP) to treat the noise signal and generate anti-noise. This offers quite a bit of flexibility, since DSP algorithms can be tweaked via software, even after the headset is built. But using DSP has its problems.
First off, DSP needs more power and tends to drain the battery much faster. More importantly, DSP introduces delay into how fast a signal is processed. Incoming noise has to first be converted into a digital signal, then processed, and then converted back to analog form to be sent to the listener’s ears. This can cause a delay of up to 30 ms from when the noise is heard to when anti-noise is generated. That may not sound like much, but it can actually make a huge difference in how well the noise is actually cancelled out.
Making an analog ANC solution requires a bit more engineering expertise to get just right, but it tends to get the best results. Headsets with analog ANC have a better battery life, and – most importantly – will react instantly to changes in noise.
Like any other headsets, ANC headsets come in many different wearing styles. The way an ANC headset is worn has an impact on how well active noise cancellation can do its job.
An over-the-ear ANC headset usually works best, since it fully covers your ears and blocks out most outside sounds. It adds passive noise cancellation to the mix and filters out high-frequency noise. But over-the-ear ANC headsets also tend to be bulkier and heavier, so some people opt for lighter options.
On-ear ANC headsets are lighter and can be more comfortable. They often come with soft cushions that sit on your ears without fully covering them. But that also means they let in more outside noise and leak your music out at the same time.
In-ear earbuds that are placed directly in your ear can also work well in combination with ANC, since they block out a lot of the outside noise. They’re also small and easy to carry around, but not everyone finds it comfortable to have earbuds stuck in their ears.
Now let’s imagine the designers have gotten all of the above juuust right. Hybrid ANC? Check. Finely tuned analog signal processing? Check. Over-the-ear design that blocks out most outside noise? Check!
Guess what? They’re still not quite done yet. You see, no matter how perfect the ANC setup is, it’s still just a small part of what makes a great headset. That’s because…
Let’s face it: You’re not buying an ANC headset for its noise cancellation alone. If noise cancellation was all you cared about, you’d get yourself a pair of heavy-duty construction ear muffs. When you buy a headset, you also want your music to sound great. But there’s almost always a trade-off between great noise cancellation and great-sounding music.
For example, to get the most out of passive noise cancellation, designers could make the ear cups fully seal off your ears. This would let almost no external sounds through. However, this would also trap lots of air inside the ear cup, so the speaker diaphragm would have little room to vibrate. As a result, you’d be left with a weak bass. This might work for classical music aficionados, but is hardly great news for R&B fans. To account for this, some headsets include a special vent that lets this trapped air escape, leaving the speaker more room to vibrate and greatly improving the bass performance.
Similarly, cranking up the active noise cancellation may succeed in canceling out more external sounds. But poorly designed headsets with cheap ANC microphones may also generate more unwanted white noise. Some observers have even gone as far as to claim that ANC is all about simply generating this white noise to drown out other sounds. That’s wrong: White noise is an unfortunate side effect, and engineers go to great lengths to reduces this white noise by using quality microphones and meticulous acoustic design.
If you only wear your headset to listen to music, the above can be enough. But if you intend to also use your headset for calls, there are even more things to take into account. You’d want the call quality to be top-notch and for the people you speak with to hear you clearly. Headset designers may consider noise-cancelling microphones and maybe even add a boom arm that can be placed closer to your mouth to capture your voice better.
As I’ve argued over the course of two articles, there are many variables that make a great ANC headset. Getting them right isn’t a simple matter of taking some miracle ANC tech off the shelf and throwing it inside a headset. The best ANC headsets on the market put all of the variables together into a design that truly works – combining active noise cancellation, passive noise cancellation, and professional microphones into a solution that suppresses noise while also making sure that the music and conversation quality do not suffer.