So, I have this very odd issue. And it seems to be regarless of ROM. Anytime I use google voice search or make a voice call, after my M8 switches back to music the play back sounds almost like I am listening it through a fan. And the weirdest part is that it doesn't matter if it is hard wired or through bluetooth (either way using a bluetooth handsfree for the voice portion). Anyone else had any similar issues? Ironically I am pretty sure my M7 and maybe even my One X had similar issues.
In terms of set up, I use an LG HBS730 Aptx Headset for hiking and walking to work, then a pioneer bluetooth enabled car stereo but I hardwire for the music (calls switch over to bluetooth). Both have the same issue. Only way to fix is a reboot.