Silent focus on Nikon d5100?

I have a Nikon d5100 and use it for movies- when I'm using the AF-S 18-55mm lens the noise It makes when in auto focus mode is quite loud. Is there any way of getting the focus to be silent? Weather it's a setting or a new lens? (I'm in no way a professional photographer so apologies if this doesn't really make much sense! If you could tell me a setting or lens or whatever I would be very grateful!)

Autofocus isn't silent. It works by means of a tiny motor, so there will always be some noise. The only practical option is to switch the lens to manual focus, and practise smooth focus-pulling as much as you can.6

All DSLRs with AF on video have this sort of problem to some extent. DSLRs are not really optimally designed for good video.

I've heard that you can reduce noise quite a bit by using an external microphone and adjusting the manual gain control, but if that's not enough you will have to turn autofocus off when videoing and focus manually. I don't know of a quieter lens, but if there's one it won't be cheap!

Better still, buy a dedicated video camcorder. Even a £200 Panasonic SD80 should give you better results.

Since you mainly record videos, you should trade the 5100 for an actual camcorder.

The video feature on the 5100 (and all other DSLRs) is just a gimmick.

Use manual focus.

This is one of the reasons why in the professional arena sound is recorded using a directional microphone which will be deaf to the noise of AF, and often focus will be pulled manually anyway for precision.

So therefore I advise you to do the same, get a mic which blocks the noise out or manual focus.