(Off Topic) Noise from battery supply

Hi Everyone
I need some help on how the remove noise from my power supply.
i am using a Max667 Low drop out regulator with my pic circuit with is used as a frequency measuring circuit .
My circuit works perfectly when i run it from a bench power supply in the workshop using about 6 - 6.4v
but when i now use 4AA batteries giving me about 6v my measuring circuit gives my wrong readings .

What is the best way to remove this noise .

Clare

How are you measuring the frequency? Its very unlikely that noise will be coming from batteries. Usually its the other way around, -power supplies have noise from their rectification of AC / regulation etc and batteries give a nice smooth output.