Reviewers of audio equipment must, as a matter of necessity, talk about somewhat abstract concepts like “dynamic range.” These terms aren’t often very well defined, but are important nonetheless. Dynamic range, which in principle simply defines the difference between the background noise level of a product and the loudest sound the product can reproduce, is a particularly significant case example. Music, of course, consists of sounds, but these sounds differ not only in pitch and combination and timing, but also in level, or what we commonly call “volume”. The ability of a piece of audio equipment to reveal the sounds at all sorts of different levels is of paramount importance to accurate music reproduction, just as the ability of audio equipment to present correct pitches and tone colors is important.
Now an important point here is that dynamic range isn’t mainly about the ability of audio gear to produce loud sounds. One reason for that is that, at most frequencies, producing loud sounds is actually fairly easy. But even if we view producing musical peaks as difficult, we still have problems at the quiet end of the volume spectrum. The problem is that music requires the ability to go from soft to loud and back again. The contrast between loud and soft is part of what gives music its dynamism. The difficulty is that we can’t simply create dynamic contrast by cranking the peaks up to super loud levels. That’s because very loud sounds are unpleasant (and ultimately cause hearing damage). So, to create dynamic contrast, we need the ability to play loud and soft. In addition, the ability to play soft sounds is key because two other essential music elements lie at the soft end of the spectrum: overtones and spatial reflections.
Once we move outside of a dedicated listening room environment, we double down on the problem of reproducing soft sounds. Not only do we have the challenge of actually reproducing small signals (not as easy to do as you might think due to friction and electronic noise), but we also have the problem of external sounds. As I sit writing this, I’m in my office. The HVAC system is coughing its way along attempting to warm the room on a frigid day. Trucks and cars buzz by outside. Take that scenario outside of an office and it just gets worse. You have train clatter, jet engine noise, and people chattering.
With in-ear headphones, some background noise reduction can be had via a seal between the headphone and the ear canal. But you can also purchase noise-cancelling in-ear headphones, with the case in point being the subject of this review: the Audio-Technica ATH-ANC23s with QuietPoint technology ($99.95).
While relying on a seal to block external sounds is simple, the extra effect of electronic noise cancellation should allow greater noise reduction and could also help tune the noise reduction to particularly difficult frequencies (e.g., the 125 Hz drone of an aircraft engine).
Audio-Technica claims that its QuietPoint technology, as used in the ATH-ANC23, attenuates "up to 90%" of the external noise from the environment. It uses battery-powered circuitry in a small box that is attached in the middle of the headphone’s signal cable to do the noise cancelling. (For those of you permanently on the go, it may be helpful to know that the signal processing circuitry is set up so that the headphones continue to work in passive mode even if the battery runs out of power.).
The ATH-ANC23 is designed for use with mobile devices. The cord is quite short, at around 1 meter, and is really optimized for a media player that is carried with you or perhaps attached to your clothing. The headphone’s impedance is 32 ohms, which makes these Audio-Technicas appropriate for use with iPhones and the like. The claimed sensitivity is 105 dB, but with no input level specified (this is a pretty common but unhelpful practice, since it more or less renders the sensitivity rating meaningless). However testing showed that an iPhone 4 could easily drive the ANC23 to satisfying volume levels and beyond.
The active-plus-passive noise cancelling approach allows part of the value proposition to aim at ease of use.
First, by relieving the earphones of the need to block out all external sounds through tight-fitting eartips, the ANC23s don’t have to have quite as tight a seal to the ear canal. This should allow the designer to create a more comfortable earphone, at least when compared with those models that create pressure points (a common problem). I’d say that the comfort level of the ANC23 is above average. As I’ve mentioned before, my in-ear comfort reference is the Klipsch Image X10i, and I’d say the ANC23s are about 80% as comfortable. However, the oval shape of the Klipsch earpiece still distributes pressure more evenly, while the Audio-Technicas seem to achieve a stronger seal, at least with my ears. Note that Audio-Technica supplies several sizes and types of ear tips, so your mileage may vary.