Recently the mic on my iPhone 4 stopped working properly. When I put it on speaker during a call, people could barely hear me. Strangely, when I made a voice memo, my recording was audibly clear? I thought for sure it was a hardware malfunction, but the fact that I could record a voice memo then made me think it was a software glitch.
I tried everything from restoring and backing up to bringing it in to the Apple Store, only to have them tell me I needed to, yes, buy a new iPhone.
Here is the stupid solution: Take a sewing needle and push the pointed end through the tiny noise cancellation mic hole next to the headphone jack (but not all the way through). Don’t worry, the hole is so small you most likely will not be able to get much of the needle head in.
After that, take a vacuum cleaner to the hole and headphone jack, viola!
There must have been some lint buildup causing the noise reducing mic to cancel virtually everything out.
It amazes me how many useless other fixes seemed to bubble up on Google.