I picked this up from this thread. I believe this can be used as a test to see if it is the Audio Chip IC that is the problem,
Turn your phone off. Then turn it on again, put pressure on the screen as shown in the image as the phone starts to boot. This will press the audio chip on to the circuit board. If the phone boots normally, it is the the Audio Chip IC.
[image|1759360]
Here is the link to the article as posted earlier.
http://www.fixstop.com/blog/iphone-7-stuck-at-apple-logo-reasons-and-how-to-fix/
'''More Tests''' :
* Open FaceTime
* Start dialling someone. When the phone starts to dial, press in the same place. If FaceTime works, then once again, it is the Audio Chip IC.
* Try a normal phone call, as soon as the phone starts to dial, press in the same place and see if it works, if it does, it is the Audio Chip IC
* Other tests you can perform, Record a video front & back & press the screen, Record a Voice Memo & press the screen
Hope this helps.