Here's the way that I have handled ill mannered 'background noise'.

I announce, "Here's a song that my Dad used to sing to us kids when we were very small"

(this song is sung very quietly except for the words quiet and riot which are shouted)

We must be ever so, ever so QUIET!
shhh! shhh! shhh!
don't make a noise it will lead to a RIOT!
shhh! shhh! shhh!
can't you hear the tick of the clock
dickory, dickory, dickory, dock
We must be ever so, ever so, ever so, ever so, ever so, ever so, QUIET!