In 2020, seemingly ever headphone manufacturer under the sun now offers noise-canceling headphones. While they come at a variety of qualities and price points, the Bose Headphones 700 are some of the most well known, and sit at the head of the pack.
But active noise-canceling (ANC) isn't a necessity for a good pair of cans. Some classic and well-loved headphones don't have this feature. The Sennheiser HD25, for instance are beloved by DJs and very often put to work in very loud environments. But while they do block out outside noise, they do it entirely passively. So what's the difference?
Active noise cancelling eliminates sound, passive just blocks it.
Active noise-canceling headphones like the flagship Bose Headphones 700 get their name because built-in technology allows them to "actively" seeks out and destroys ambient sounds before they reach your ears. These headphones have miniature microphones in each ear cup that listen to ambient noise frequencies coming from outside the earcups, and they then electronically generate the exact opposite sound frequencies — these are called antiphases — that effectively “cancels” out both sets of sound when the soundwaves physically collide. The result is that you only hear the music. Active means that the headphones have a built-in battery that’s dedicated to powering these noise-canceling microphones.
Passive noise-canceling is a slipperier term that is sometimes used in marketing, but is more accurately referred to as noise-isolating. These headphones use their natural shape and materials to block out ambient sound. Passive noise-canceling headphones don’t have any powered microphones or built-in technology that actively seeks out and destroys ambient frequencies. In fact, they don't actually have to be powered or have a built-in battery at all. Anything that physically covers your ears, like ear muffs, is able to isolate noise and can be considered to be "passive noise-canceling."
Active noise-canceling headphones tend to sound worse.
There's a reason why most many high-end headphones often don't have active noise-cancellation. -- it takes away from the overall sound quality. In order to effectively cancel out ambient noise-frequencies, noise-canceling headphones need to add their counter frequencies (antiphases), which adds noise and ultimately leads to sound degradation. That is why professionals like DJs, even though they are working in a very noisy environment, might favor cans like the HD25 which won't muck up what they're hearing with active cancellation.
The good news is that most noise-canceling headphones like the Headphones 700 give you the option to turn ANC on or off. This is ideal for when you're listening to your headphones in quiet environments. But because ANC headphones can generally rely on their microphone superpowers, they generally don't offer as much passive isolation as non-ANC headphones do. If you have any pair of ANC headphones, try toggling the noise-canceling on/off and hear how it affects sound quality.
Active cancelation puts pressure on your ears.
Active noise-cancelation doesn't just effect the way the music sounds, it also affects your ears as you listen to it. When switched on, the soundwaves that active noise-canceling creates a pressure against your ears that's similar to what you'll feel while driving through a tunnel or ascending to cruise altitude in an airplane. It's not a painful sensation, but it is a noticeable one, and one that some people find unpleasant over extended periods of time.
So which one is better?
It depends, of course, but we generally recommend active noise-canceling for the average person. The upsides -- being able to hear your music better at lower volumes -- generally outweigh the downsides. The calculation can be different for edge cases and professionals, who either demand extremely high-quality and unadulterated sound, or who are going to be wearing their headphones for extremely long stretches of time day in and day out.
But overall, for the average listener, ANC helps you focus on what you're listening to, and that's great.