When do you say this? And how do you say it another way?

Can you just take it down a notch?

Question

When do you say this?  And how do you say it another way?

Can you just take it down a notch?

Answer

It means, in a very polite way, that you are being asked to be quieter.
An alternative: please be quieter. Or p
: please turn down the volume. (Even if you are the one making the noise with your voice. )  Or other phrases in this vein.