Aidan (9 yrs) and Danny (10 months) get like that at times, so it's not unique. I've found that different kids at different ages need different techniques. Especially when they start getting immune to your methods!

With Aidan, nowdays just raising my voice above his and saying "how many more people in the world need to hear me telling you to be quiet?" works because he knows he can't out-do me and anyone within about 100 metres just heard him get into trouble and he doesn't like that at all... but I know how to project my voice to the point of being far louder than his without actually screaming. A few singing or stage drama lessons can teach you that trick. Other techniques that have worked over the years have been to turn off everything else that is making a noise - TV, stereo, toys, etc - and then the only noise is Aidan and he couldn't use background noise as an excuse anymore and became embarrassed that he was being so noisy. Just standing there and staring at him coldly in silence until he noticed and then coldly ask him if he's finished yet, that used to subdue him into silence for a while. Turning the stereo on and pumping up the volume to totally drown him out - especially good if using music he wasn't so keen on - used to drive him nuts and he'd then be screaming at me to turn it down, at which point I'd do so and tell him I only turned it up because I couldn't hear it over all his noise. These things have all worked for a little while at different ages and stages with that boy.

However, with Danny I've so far always had to take the opposite approach and get in front of him and very quietly say "shhhhh whisper" repeatedly and he stops screaching and starts to copy me. This never worked with Aidan however. Distraction didn't work with Aidan either as he'd just find something new to get over-excited and noisy about!

Distraction is best.  Maybe dropping a money tin on the floor or stand where they can see you and mime what you want to say.  The bigger the gestures, the more they are going to wonder what it is you are trying to do and forget they even have a voice.  Worth a try.

I go up to them and blow it and they both stop and look at me after they have quickly stood to attention....Then I am able to communicate with them whilst they are quiet....Some times they also do not realise how bad they sound and they know that when I blow the whistle that they have really crossed the line..

We also have a no screaming in the house rule and if they start screaming I ask them where do we scream and they tell me at the clothes line...I ask them if that is where they need to go and if it is out they go...

Hope you find a way that works for you as I know how hard it can be (especially whilst feeding bub)

Cheers Spinnychic