Thanks for the replies so far - the aircraft is a B757. It can be pretty noisy on the flightdeck. Personally I wouldn't want to have the headset off during the cruise, although some do. 99% of the conversation is over the intercom, unless there's someone else on the FD.
Rainboe,
Interesting story - I'll have a gander at the the Lightspeed Zulu now...my only slight concern would be that I haven't come across the brand before but that's probably my shortcoming!
B&S