The first thing I would recommend would be to check the "Voice Volume" settings in the Preferences menu - Sound.
Also, just to rule out any issues with the client files, please run a repair function on the launcher. To run the repair, please log in on the launcher, select the cog shaped icon and then the repair function.
Please don't hesitate to come back to us if you have any further questions.
I can attest that it isn't related to broken client files as I experienced the issue (only on one of my characters) and ran the repair function. The repair found no issues. It issue started after the 1.7 patch.
WE ARE TIRED of being told to run the client repair tool.
Fix the bugs.
Test the code before rollout!
Actually do something with our in-game tickets.
Provide updates on issue resolution. Don't just close the ticket.
We the paying player base expect a professional service. Communicate with us don't just fob us off.