Causes of FaceTime Audio Not Working
FaceTime Audio might not be working for various reasons, yet the most common is that you don’t have a compatible device or operating system. In particular, this applies to any iPhone older than the iPhone 4 (e.g., iPhone 3) and the first-generation iPad. Other possible reasons why you don’t have audio in FaceTime include:
Your microphone is muted or malfunctioningYour volume is too lowAnother app is using your microphoneYour iPhone is out of dateProblems with your internet connection
What to Do When There’s No Audio on FaceTime
Try these fixes in order until FaceTime audio is working. Also, if the person you’re speaking with is complaining that they can’t hear you, you should check that you haven’t muted your microphone. If you can hear and record your voice using such tests, your microphone is working fine.