Zafira DTI 04 noise from engine bay when coASTING or de-accelarating?

bought car a couple of days ago yesterday noticed a noise from around engine bay, not on tick over or or when accelarsating usually around 1-1500rpm if you rev engine you can hear or when driving and your de-accelarating especially with window open near awall etc. thbe sound is like a fast tapping noise taken to garage they they would have to strip down to source problem any ideas????????.