The new Sun Chips bag is the loudest we have come across and it is off the chart. Made of all-renewable materials (which is a good thing), this bag sounds like you are breaking glass when you handle it. It can be heard perhaps 30 feet away even with subtle background noise. Good luck trying to sneak snack on some of these at the office or home.
SunChips is not alone here in the ongoing loud packaging problem. Keebler cookies and their flimsy plastic tray - sounds like a freight train when you try to push tray back into the bag. The new Oreos package which has this rip-flap deal on the top is also a noisemaker.
There are many others and the staff here at the FPT is compiling a database and noise scale chart that will be posted here shortly. In the meantime - speak out against loud packaging - sneaking a snack should be a quiet personal moment.