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.).