I have spent hundreds of hours teaching pilots to use a high level of discipline in the use of intercom in such circumstances. The background noise created when one of the pilots involved keeps an "open mike" is considerable. So, it is vital to use the intercom/transmit switch in the off position unless you have something vital to say and then, as soon as you have said it, switch off again.
This is particularly essential when reading and responding to checklists.
stretching the thread a bit ... but I've seen minor problems turn into major problems when O2 masks interfered with normal communications on an emergency return due to smoke in c0ckpit