Info on Telex ANR headsets...

[midlifeflyer]

The passive noise reduction seems really good

I noticed that in my 50D as well. On my third short flight last week I forgot to turn them on and never noticed (I was also flying a quieter airplane).

 

[MOCHA HAGoTDI]

Just got back to an internet connection. Even after charging the batteries, the thing was still acting up (it's like the noise canceling was "thumping" on and off).

After replacing the batteries, all's well. It's amazing how quiet it is when the NC is turned on!