Microphone number 2 issue not working

[Ghyathoo]

After the last update the second microphone in my Lumia 1520 not working any more such as phone calling and Cortana the microphone not working only the recording microphone working ..so how I can go back to WP 8.
The only,way to me now using Bluetooth headset since last update so until when I'll stay using headset

 

[wasim sallam]

try to clean the mic hole.
I had the same with 920 and it worked for me