to use AH voice (built in) you need to do a few things.
first off make sure the keys are mapped properly. the default AH keys are:
F12 - range voice
T - channel voice
they work as follows:
"Range" voice is activated by holding down the F12 key and talking into your mic. anyone within approximatly 6000 yards fo you will hear what you transmit. this channel is not tunable it is on by default
"Channel" voice is activated by holding down the T key and talking into your mic.
tuning the radio works like this:
channels 101-199 are for anyone in your country. anyone on the same channel as you will hear what you transmit as long as they are in your country, no matter what distance away on the map.
channels 201-299 global voice channels. if say you are a knight tuned to channel 203, and a bishop is tuned to 203 you will be able to converse with each other.
Channel radio can also be set to "Squad" "mission" or to an individual player's CIPD. if you tuen to say "JB73" only i will hear what you say, and i would have top manually tune to you to talk back.
this tunable channel vox is radio set 5. the default key command to change it is:
.radio 5 XXXXXXX
where XXXXXXX is what you want it set to.
you may also hit / bring up the radio buffer, and manually insert the frequency, or use the drop down menu.
in game there are some other vox features under the setup / preferences / voice menu
enable tunable and range beeps is where you hear the "beep" when someone starts to transmit.
the volume sliders are:
mic volume - your mic volume
play volume - how loud you hear other peoples vox
effect volume - when someone talks, you can have the games sounds cut out fully, or just a bit, or none at all.
hope that all helps