He means the speaker on the back of the phone, watching netflix on the device. I had this issue yesterday at max volume and one click lower. I usually don't watch movies on my phone but I'm hoping it's just with Netflix. Have not had it happen listening to music of any kind or playing games.
I had this issue while watching a video yesterday. When you turn it up you hear it even more. I think the speakers can't handle the loudness. I adjusted my audio settings and it got better but I could still hear it. I haven't tried turning off the EQ all together yet. I currently have it on Vocalizer.
The issue is with the Netflix app. I experienced this on my Bionic as well and had my co-worker test it on his OG Droid. His phone had the same popping noises. They were not there before the most recent Netflix update. Hopefully Netflix can get this resolved with their next update.