Frito-Lay makes a lot of noise marketing its Sun Chips snacks as "green." They are cooked with steam from solar energy, the message goes.

But its latest effort—making the bags out of biodegradable plant material instead of plastic—is creating a different kind of racket. Chip eaters are griping about the loud crackling sounds the new bag makes. Some have compared it to a "revving motorcycle" and "glass breaking."

It...