Soundproofing an existing extension

[livvyliv]

We have recently moved in to a house with a fantastic 2 storey extension,apart from the soundproofing.if you're sitting in the lounge and the kids are upstairs or using the bathroom,you can hear absolutely everything.what is the best(cheapest)way to soundproof?is there a quick fix?by the way it has carpets already.
It's really,really irritating me.
Thanks

[tricot39]

Could you fit a separate ceiling below the existing using an acoustic ceiling board?