Screeching 3 year old

[Candycandle]

My middle child screeches. He does so when he's happy, excited, scared or annoyed.
We recently moved into a rented property, the neighbours came over an hour ago to say that they are fed up with the banging and screaming. I can try stop the banging (he enjoys throwing and dropping toys)... But as for the screeching. Every attempt hasn't worked.

I thought he would grow out of it but it's got worse as the summer holidays have progressed. His elder brother winds him up and they've spent more time together than ever recently which doesn't help. I can take them out and it helps the screeching but I can't keep them out the house 24/7. Letting them out in the garden makes his screeching worse as he seems to think he can ramp it up a knotch.
Whispering to make him quieter doesn't work.
He will even screech if his favourite programme comes on tv.
I'm at at a loss. I'm embarrassed and I'm confused at what I can do other than say no or let him grow out of it.

Please help

[VioletBam]

Is his language on track?