For the new folks who do not yet have a microphone (and yes, you should get one...) and have little free cash...
Here are two extremely inexpensive options from WalMart for your consideration...
(No relationship to @WalMartGreeter whatsoever...)
One is a headset ,one is a freestanding microphone.
These options are less than $10 (plus any shipping if applicable)
There are lots of other possible solutions out there including Sony earbuds with an in-line mic, etc. for less than $10.
For squad play in VCO, we strongly suggest you get a mic.
It allows you to quickly communicate with your squad leader (we usually are too busy to read messages in the message box on the screen) and other members of your squad/platoon.
It makes both you and your entire squad more effective to be able to quickly respond.
It also lets you easily ask for clarifications on anything you didn't catch or understand in orders.
It lets you ask general game questions during lulls in the action and gets you answers accurately and quickly.
VCO OPS are all about speed and quickness - this helps you achieve that.