iphone xr microphone issues

hi everyone, I am experiencing quality issues with the microphone of my iphone xr.

specifically, when I am on a phone call with someone and I tap my screen, the other person can hear the tapping sound quite loud.

also, occasionally the quality of my voice drops for no reason (I keep my hand away from every mic, including the one for noise cancellation).

I would really appreciate your help.

thank you