How to get your colleagues to be quiet

Does your work and productivity suffer because your office is too noisy? Do you sometimes wish your colleagues would just shut up so you could concentrate? Here are some polite ways of asking for a bit of peace and quiet in the office:

Would you mind keeping the noise down please? I need to concentrate for a minute.

Please could you talk more quietly? I can't concentrate on what I'm doing.
Or
Could you talk more quietly please?

(Note: If you say "Could you please talk more quietly" and put "please" after "could", you can show exasperation, especially if you emphasise the "please". It's as if you've already asked a couple of times, and nothing has happened.)

Can you be a bit quieter please? I can't hear what she's saying.

Please keep the noise down! I'm on the phone.

Shhhh! I can't work in this noise!