Car camera audio

[Zed 44]

I recently bought one of these off E-bay. I also have another cheaper single camera one for the family car.

http://www.ebay.co.uk/itm/321203384846?ssPageName=...

I've noticed with both of them that the audio becomes quite distorted with static the faster the car is driven.

I wonder if anyone else has experienced this and is there a cure for it?

The wires run down the A pillar around the steering column area to the cigarette lighter.