A long-running Apple Support Communities thread with 257 posts complaining of audio issues when using a pre-Bluetooth LE Mac on Yosemite reports that the issue is still present in OS X 10.10.3 and 10.10.4 Beta . The issue reportedly affects a number of machines up to and including late-2011 Macs.
I am experiencing an issue with FaceTime video calls or voice calls (using FaceTime audio or the iPhone handoff feature) where all I can hear is a strange clicking sound, like static. The other person can hear me fine and I can see them fine if on FaceTime video, but I can’t hear them.
Various fixes suggested in the thread seem to work temporarily for some, including a restart and resetting PRAM, but the issue returns.
Some in the thread speculate that OS X 10.10 broke something when Apple attempted to ensure that phone continuity features worked only on Macs with Bluetooth LE. Some have had logic boards replaced by Apple with no change.