Headsets, Inc. of Amarillo, TX makes an ANR kit that drops right into a David Clark headset or most any helmet. If you can use a soldering iron just a little, you can do it yourself. You do have to drill one hole in the dome, to allow the power cord to come out, but that's the only mod you have to do. Remove the existing speakers, & the kit drops right into the dome, and the earseals hold it in place. The existing wiring is soldered to the kit parts.