Audio Files: What Noise-Canceling Headphones Can and Can’t Do

The work-from-home trend has brought families and roommates closer than ever … for better or worse. On the worse side, many professionals are finding it hard to concentrate on their work while the kids are playing nearby, and they’re getting frustrated when the noise from ever-present family members makes it hard to hear their jazz albums. Many commercials and tech columns suggest noise-canceling headphones as a solution—but they wrongly assume noise-canceling headphones cancel all noise. The reality is, for much of the noise you probably want to cancel, noise-canceling headphones are no more of an effective block than standard headphones and earphones are, and sometimes not as good.

Noise-canceling headphones work by using microphones inside (and sometimes outside) the headphones to pick up noise. The audio signal from these microphones is then reversed in phase, so a positive signal becomes negative and vice versa. This signal is blended with the music, so the headphones produce a phase-reversed version of the noise that cancels out the actual noise.

The problem with this system is that noise entering the microphone, then being amplified and sent into the headphones’ speaker drivers, can create a feedback loop, exactly like the loud, squealing feedback you hear when a microphone gets pointed at a P.A. speaker. To prevent this, headphone engineers limit the noise-canceling system’s function to frequencies below about 1 kilohertz. That means the noise canceling will work on the deep fundamental tones of voices and most musical instruments, but most of the upper harmonics—the frequencies most critical to understanding human speech—will slip right past the noise canceling.

Fortunately, frequencies above 1 kHz are easy to block with physical obstructions, such as the shell of the headphones and the silicone tips on the ends of most earphones. So ordinary headphones and earphones can block these higher-frequency sounds about as well as most noise-canceling headphones can, and occasionally better.

In Your Quiet Place

A couple of years ago, I did some technical tests to find out which types of headphones and earphones best block which kinds of noise. There’s no question that noise-canceling headphones are the best at blocking low-frequency noise, such as the droning of jet engines heard inside an airplane cabin. But while some models can almost completely eliminate the sound of airplane cabin noise, others have close to no audible effect. 

Good noise-canceling headphones tend to be fairly expensive. I’ve measured the noise canceling on most of them, and the best I’ve found are Bose’s $379 N700 NC and $329 QC45. The only inexpensive model I’ve found that can compete with these is the $129 Soundcore Life Q35. 

However, there’s a downside to excellent noise canceling: It can produce a phenomenon I call “eardrum suck,” in which your eardrums feel an uncomfortable sense of pressure, like you do when ascending in a high-speed elevator. The Bose N700 NC and Soundcore Life Q35 have adjustable noise canceling that can eliminate this effect.

While these headphones do a pretty good job of blocking the sound of voices, my tests show that some earphones can block voices just as well, and sometimes better. The best results are generally obtained with earphones that are custom-molded by an audiologist to fit your ears. These are commonly worn as stage monitors by touring musicians, and they’re available from such companies as Westone and Ultimate Ears. Because they fill your ears so well, they block most of the sound of voices.

A less expensive alternative is “universal fit” earphones that route their cables back over your ears instead of downward, such as the $99 Shure Aonic 215 and the $249 Sennheiser IE 300. These earphones fill your ear in much the same way that custom-molded models do, and their noise-blocking performance can usually be greatly enhanced through the use of foam ear tips instead of the usual silicone rubber tips. Some earphones include these tips, but they can also be purchased from Comply Foam, Dekoni, and others.

Another affordable alternative: headphones designed for musicians who play loud instruments—most commonly, drummers. One example is the $170 Direct Sound Studio Plus+. It’s designed to be noise-blocking rather than noise-canceling, and I’ve found it blocks higher frequencies of sound almost as well as the earphones cited above do. In fact, I use a set of Direct Sound headphones as hearing protectors when I do my lab measurements of noise-canceling headphones, which require me to play very loud noise from an eight-speaker system.

Whenever I fly, I always bring a set of noise-canceling headphones, and whenever I visit my family or plan to be in a noisy office, I bring a set of universal-fit earphones with over-ear cable routing. Whether you choose one or both, I think you’ll find that listening to your jazz albums through headphones can be a lot more enjoyable—because the lower the noise, the more clearly you’ll hear the softest breaths of Cassandra Wilson, the subtleties of Jack DeJohnette’s cymbal work, and the lightest touch of Bill Evans’ right hand.