Loud Static Noise Coming from IPhone

Hello! I've had my IPhone 7 for a while. Lately I've been experiencing fast battery loss (only sometimes - though I understand that my phone is old and I'm frequently on it) and I've been hearing some noise coming from the speaker of my phone even when it's not in use (I would have to put it to my ear to be able to hear the noises).

The noises would be static (mostly), and then there would also be screeching noises and occasionally small tapping. I don't know how long it goes on for, but it usually happens when I go on my phone and click on a video or just simply type a text. I always end up powering off my phone but when I turn it back on, the sound would sometimes remain for a few seconds.

I've tried factory resetting my phone before and restoring my iCloud information twice, however I can still hear the noise and it frustrates me so much because resetting and restoring took me a while :(

Can anyone please help me fix my problem? What is happening to my phone and what should I do to stop the noises? This is making me paranoid.