I Looked up the specs for my iPhone 4. I read tons of blogs and everyone said they diner know how to fix. Well with everything to gain I decided to tap and press around on the back of the motherboard as if I was doing brain surgery while making a call to customer care. Well Houston if there's a JLu there is a way. I found the sweet spot. When pressure is applied right below dock and mic flex and above the wifi antenna suddenly the mic began to work. I used battery packaging cardboard in a small L shape then slid the lid back on and screwed the back cover back to phone. And voiala! A mic hack fix for iPhone 4g is born! Hope this helps you!!!!!! Thanks for watching ! Jonathan Luke