Most people imagine “noise-cancelling” headphones as headphones designed to reduce the perception of unwanted sound by their wearer. Whether it’s a baby crying on an airplane or that annoying coworker incapable of using an inside voice (sorry, Schox team), people usually turn to noise cancelling headphones because they’ve decided that gouging out their eardrums is not a viable method for addressing sonic distractions.
And, to some extent, noise cancelling headphones are a viable solution; however, they are far from the best solution in most cases.
Noise Reduction: Cancellation + Isolation
To understand why noise-cancelling headphones aren’t great for most people, we first need to understand what “noise cancelling” means. Above, I posited that people may interpret noise cancellation as “reducing the perception of unwanted sound” (i.e., noise reduction). In fact, noise cancellation is a very specific type of noise reduction, and it comes with some important caveats.
Noise cancellation refers to the reduction of noise via destructive interference; in particular, noise-cancelling headphones work by sampling environmental noise with a microphone, generating a noise-cancellation signal (basically, a phase-inverted copy of the noise), and playing this noise-cancellation signal to cancel the noise perceived by the headphone wearer.
That sounds great! So what’s the problem? Besides the obvious (that this solution requires power), generating a good noise-cancellation signal takes time. The consequence of this and other effects is that noise-cancellation headphones tend to work well only for cancelling slowly-changing low-frequency noise; for example, the drone of an airplane engine. In contrast, the piercing shriek of the baby that airplane may be carrying is largely un-dampened by current noise cancellation techniques.
Thankfully, noise cancellation isn’t the only option for noise reduction; quiet-seekers may rely on the low-tech but venerable solution of noise isolation. That’s a lot of fancy words for sound absorption, e.g., as provided by earplugs.
Noise Isolating Headphones
You might be wondering- if noise isolation is so great, why don’t you hear more about it? The short answer is marketing (look to the computer industry to see a similar trend in processor clock speed). Another contributing factor is that the best noise isolating phones, in-ear monitors (IEMs), require you to insert the IEMs into your ear. In addition to the psychological issue some people may have with this, the reality is that inner ear shapes vary much more significantly across people than outer ear shapes- meaning that a person may need to try multiple earbuds to find a good fit.
There are two responses to this: 1) IEMs are much easier to fit than most realize and 2) there are still great non-IEM options (i.e., good noise-isolating over-the-ear headphones).
IEMs
Primarily, IEM fitting is determined by the tip of the IEM (which is almost always changeable). While there are hundreds of tip types, I have found anecdotally that the vast majority of people can find an extremely comfortable fit with either the small or medium size of the Shure Olive tips. If your ears are especially small, start with the small- otherwise stick with the medium.
These tips are compatible with a number of IEMs ranging from inexpensive to high-end. Here are some good examples (links go to Amazon):
Etymotic HF3 (what I use) $140
Etymotic HF2 (same but for Android instead of iPhone) ($149)
Shure SE112 ($59, iPhone)
Klipsch S3M ($36)
Klipsch R6m ($59)
Note: the above are all wired headphones and have microphones / remotes. There are versions without mics/buttons as well. There are even solid bluetooth options compatible with these tips: Klipsch R6 Bluetooth ($69)
Over the Ear
A good IEM is much better at noise isolation than any over-the-ear headphone, but there are still some good options in that area for those who can’t stomach an IEM. A particular standout is the Audio-Technica ATH-M50x, alternatively, the Shure SRH440 is also excellent.
The Numbers
I’ve been speaking qualitatively for convenience, but if you’re curious about the numbers, the best noise-isolating headphones (IEMs) are capable of reducing external noise by up to 42dB- bringing a normal conversation down to the sound of quiet leaves rustling. The over-the-ear headphones I mentioned are capable of reducing about 35dB of noise. And, just for fun: the Bose Quiet Comfort 2 noise cancelling headphones? At best, they hit 35dB of reduction but only for very low frequencies; at vocal frequencies, they are only capable of reducing noise by 25dB. In other words, the IEMs substantially more effective at reducing noise (and cost a fraction of the price).