Speaker gives loud whine to others on calls?

My wife's iPhone 4 has started giving this loud whining noise when she receives or dials out on a call. It's only heard on the other line, not hers. She cannot hear anything. She can talk on headphones and speaker. I have tried resetting, plugging/unplugging headphones, working with volume buttons, slightly tapping around speaker area, etc. I performed the ifixit guide for earpiece speaker replacement. Guide was great! I didn't tear/mess anything up. Everything still works, but speaker is doing the same thing even with the new piece. Please help!?!