Frito-Lay’s PepsiCo unit is facing a viral backlash over the new, compostable bag for its SunChips grain-based salty snacks. Complaints that the bag, made of polylactic acid (PLA), is excessively noisy when opened and handled, have taken on a life of their own on the Internet. Facebook pages have sprouted with titles like “Sorry, But I Can’t Hear You Over the SunChips Bag” and “New, noisy SunChips bags make me hate the Earth.” The Wall Street Journal devoted an article to the controversy last week. Frito-Lay is trying to roll with the punches, attaching signs to some store shelves that read, “Yes, the bag is loud, that's what change sounds like.”