I have a pair of ATH-ANC7b by Audio Technica, most of the noise canceling happens from noise blocking. The noise canceling (using phase inversion) is only moderately effective, best on consistent tones.
Basically if you want to simulate the effect, grab a pair of ear plugs and put on your headphones and turn off and on your headphones, I doubt you'll hear much of a difference.
The most effective noise canceling/noise blocking headphones use the double or triple flange inserts that tend to come with Etymotics or higher end Klipsch earbuds. The Etymotic Research triple flange tips (not the most comfortable) claim 35-42 dB, having bought (and later returned a pair) I can attest they're far far more effective than any noise canceling technologies. In fact, they're more effective than most shooting ear protection, which usually drops about 28 dB. Also its important remember, that noise blocking/canceling is more effective on shorter wave forms as they carry less energy, so deep bass signals will be the hardest to to effectively block. If you have inconsiderate person blasting bassy music all hours, almost no amount of hearing protection/noise canceling will block all of it out.
The secret of noise dampening/isolation is dead air, and a triple flange design gives you two dead air chambers. The double flange designs give you one dead air chamber.
If you're looking for extreme noise isolation, simply wearing any close air earphones combined with in-ear monitors will provide more sound blocking as you're adding another layer of dead air. If you're looking for the most effective noise isolation, Etymotic Research is it. Covering your ears with your Audio Technica will undoubtedly add yet more noise blocking, but most because of the physics of headphones creating a seal around your ears. You'd like be better off buying earphones designed for hearing protection combined with earbuds than the ATs specifically.
