Hank,
I have a slightly similar (and older) set of Sony headphones similar to what you bought. You're gonna love em.
It's actually pretty spooky when you put them on. They cancel out a LOT of noise! Truth be told, if the wife's vacuuming or whatever while I'm editing a video, I'll go grab them and use them, and all is well.
Nothing will eliminate 100% of the noise, but these do a great job. The reason I actually bought the set I have is because the church I worked for used them with the camera that was in the middle of the orchestra pit (big church-they had a full orchestra every Sunday!). With those mics on, you could still hear the sound that the booth was feeding your earphons even with the instruments being all around you.
They also give you a great excuse when the wife accuses you of not listening "Oh sorry hon. Had those headphones on again!" :D
The one downside for me is that my ears seem to perspire a lot in these headphones. We did several outdoor weddings in a row last month, during a scorching heat wave. At the end of one, I pulled off the headphones and it felt like a river flowed down my face. Minor issue, but for the quality, it's worth it.
By the way, if anyone wants to know the secret behind sound-dampening circuits, it's actually quite simple. Sound travels in waves. I.e.:
/\/\/\/\/\/\
A dampening circuit reverses the waves, giving you:
\/\/\/\/\/\/
The result is that the colliding sound waves cancel each other out, leaving you with:
------------
It's actually the same way that mufflers on a car work, except in the circuit, the reverse wave is digitally created, while in a muffler it's done acoustically by reflecting the sound off the internal cylinders in the muffler.
Okay, I though that was neat, anyway :D