For a few weeks now our otherwise great little car has started to develop a rumbling noise which sounded almost like the exhaust knocking underneath the car when you pull off and was very noticeable from inside the car. It sounded like the type of noise a 10 year old car makes when everything is getting a bit old and flabby and I was getting a little bit concerned that this would be a pita and/or expensive to fix.
Well, worry not as it took all of 2 mins to actually fix. I did do a search on here and didn't find anything apart from something on the Punto forum which suggested the air hose that comes off the air box becoming loose and that's what it turned out to be. The bolt that holds the plastic air hose to the slam panel had worked loose and fell off. New bolt and locking nut fitted and job done.
I can't quite believe that that bit of plastic could cause the amount and type of noise that it was.
Hope this might help anyone else with a bit of shared knowledge if they experience this problem on their car

Might be useful to know one day. Which engine is it?

2012 1.2 petrol