Noise-Cancelling Headphone Review: Audio-Technica ATH ANC23, Phiaton PS 20 NC, Sennheiser CXC 700

Mention noise-cancelling headphones and most people think of large, over-ear models like the Bose QC15. Comfy as those big cans can be, they’re waaaay too big to slip into a pocket or purse. But not all noise-cancelling headphones come in cases sized like jumbo donuts at the State Fair. In fact, a few manufacturers have added noise-cancelling technology to their in-ear monitors (IEMs), using a little “lump in the line” to house the needed electronics.

One might fairly ask, though: Do IEMs really need noise cancelling? After all, when used with tips that fit your ears properly, IEMs completely seal off your ear canals. However, IEMs do most of their noise-blocking at frequencies above 1 kHz. Below that, they’re not so effective at keeping the noise out.

Thus, the SOL Republic Amps HD IEMs I’m wearing as I write this are doing a swell job of blocking both the sound from the TV my parents are watching and their frequently voiced opinions of the guests on The View. But if I use the Amps HD on my plane trip home, much of the noise inside the airliner — which is concentrated at frequencies between about 50 and 500 Hz — will slip right past the rubber tips and into my ears. Yet that range of frequencies is where electronic noise cancelling works best.

So yeah, adding noise cancellation to IEMs could give you a quieter background for your music when you’re on an airliner, and maybe in a bus or subway car, too. But that’s just the theory. We wanted to find out the reality, so we borrowed samples of noise-cancelling IEMs from three leading headphone manufacturers: Audio-Technica, Phiaton, and Sennheiser. All three models use a tiny enclosure for the noise-cancelling circuitry, all three run off a single AAA battery, all three can be used with or without the noise cancellation active, and all three will work even when the battery runs down.

I ran the three NC-IEMs past a listening panel composed of me, L.A. voice actress Lauren Dragan, and S+V contributing tech editor Geoff Morrison. All three IEMs were plugged into my Rane HC-6S multi-output headphone amp. The panelists listened to a mix of CDs played on a Denon DVD-2900 DVD/CD/SACD player and MP3 and AAC files played from smartphones or iPods.

After the subjective evaluation, I ran lab measurements on all three to find out how they perform on objective tests — and, especially, to get a precise idea of how well the noise-cancelling technology works versus the IEM on its own. I used a G.R.A.S. Type 43AG ear/cheek simulator, a Clio FW audio analyzer, and a Musical Fidelity V-Can headphone amplifier. I experimented with different tips and slight changes in position of the IEMs to get the most representative results. I tried measuring the frequency response with and without noise cancellation active, but with all three models, I saw a difference only in level, not in the shape of the curve. I didn’t do my usual comparison of measuring frequency response when driven from 5 vs. 75 ohms because the internal amps in noise-cancelling headphones make the measurement irrelevant.

Last, I brought all three models with me when I flew to visit my parents for the holidays, to find out how well their noise-cancelling features worked in a real-world application. Not only did I try them on planes and on the L.A. Metro bus I took to the airport, I also recorded some of the ambient noise in one of my flights for later playback through a Genelec HT205 powered monitor, thus allowing me to replicate the sonic environment of the airplane in my home for further testing.