The Doctor and Miss Foster in “Partners in Crime”

Seeding a level five planet is against galactic law.

Are you threatening me?

I'm trying to help you, Matron. This is your one chance, because if you don't call this off, then I'll have to stop you.

I hardly think you can stop bullets.

No, hold on! Hold on! Hold on! One more thing, before, dying. Do you know what happens when you hold two identical sonic devices against each other?

No.

Well then, let's find out! [He points the two devices against each other and activates them, resulting in a loud and irritating noise.]