no sound from radio .except sometimes loud screeching Noise

Hello i am trying to work on 2105 kia Sorento radio lights up but no sound
even after hard reset. sometimes even with the radio off loud screeching.
doesn't sound like normal static. only way to make it go away is turn car off. i
was told it might be the amplifier but have looked into videos and pics. have
gotten different ideas where the amp is. two different diagrams had it in the
back wall area one had right side one had left side. didn't see any access
point for either side. if anyone has a different reason why this is happening i
would love to know. Or if amplifier sounds like the problem can someone
post where and how to get to it. thank you .Chris