push to talk headsets?

[Buffalo]

I have a relatively small 4 person office with the servers in a cabinet one end. It gets rather warm so I run a portable a/c unit at the other end with pipe out of window. There is a high amount of white noise as the cabinet has extraction fans as well as the servers, switch, etc. and it's being commented on by clients when on VoIP calls as the mic is constantly keyed.

Is there such a thing as push to talk mics for headsets? Or at least a good set that will cut the background noise. Maybe noise cancelling cans would be good too?!

Thanks

[Pachydermus]

Any decent headset should have a mute button.