Noisy pipe heard after turning off faucet- what's wrong with it?

[canon]

I've been living in this house the past year. The last two days I began to hear the pipe rattle ( or knocking sound) after turning off the single handle faucet (for cold water). It doesnt happen when I move handle to left for hot water and push it down to turn off. I would also hear another pipe rattle sound after my toilet refills. Does this mean that the riser behind the wall is not secure?

[pgtek]

hi
sound like loose pipe in the wall.
the pipe wher not secure and rattle