It seems I have the same problem on my iPhone 4
iPhone 4 iOS 5.2
FYI: No plastic cover blocking internal speaker and all Volume settings of my iPhone are up.
Problem description:
A) When placing a call, (Using internal phone’s ear piece) the volume of the “Simulated” dial tone is extremely low.
B) Once connected to the other party, the volume of the person speaking at the other end is extremely low.
C) The other party can hear me loud and clear.
This problem does not appear when:
1 - I use the earphones (headset) supplied by Apple.
2 - I select “Speaker” from the keypad to talk using the “speakerphone”
3 - I use a bluetooth headset.
Important: I realized this issue started when I upgraded my iPhone from iOS 5.0 to 5.1
In order to troubleshoot this issue:
I restored the iPhone several times with no success while on iOS 5.1
I upgraded the iOS 5.1 to the latest 5.2 but the problem persists.
I tried any workaround suggested in the internet (There many iPhones having the same problem)
I already sent a bug report to Apple about this issue.
Any idea please??