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 is louder than "the cockpit of my jet," said J. Scot Heathman, an Air Force pilot, in a video probing the issue that he posted on his blog under the headline "Potato Chip Technology That Destroys Your Hearing." Mr. Heathman tested the loudness using a RadioShack sound meter. He squeezed the bag and recorded a 95 decibel level. A bag of Tostitos Scoops chips (another Frito-Lay brand, in bags made from plastic) measured 77. 
 
 A new compostable material is being used by chip giant Frito-Lay to house its Sun Chips brand snack. The catch? It's really noisy. 
 
 Clifford A. Wood, a 69-year-old in Tempe, Ariz., posted a warning on a Google chat page for people who work in theaters, cautioning: "Please NEVER sell Sun Chips in these bags at your venue." 
 
 A Facebook group called "SORRY BUT I CAN'T HEAR YOU OVER THIS SUN CHIPS BAG" has attracted 29,949 fans, with many posting outraged comments. It's "the worst when your stoned at 2am and trying to not wake up the house," one person said. 
 
 In other circumstances, chip-related loudness is viewed as an asset. Frito-Lay has long pitched many of its various snacks as crunchy. Cheetos has used the slogan "The cheese that goes crunch!" A Doritos ad rolled out in 1989 featured Jay Leno revealing the secret ingredient: crunch. 
 
 Enlarge Image Close Associated Press It took four years to develop the compostable bag for Sun Chips. 
 
 Tell that to Mackenzie Kuhn's fourth-grade teacher. At Ladd Elementary in Fairbanks, Alaska, 12-year-old Mackenzie brought some Sun Chips to a party to mark the end of the school year. When she opened the bag, everyone looked her way, she says. 
 
 "Please try to open your bag quieter, Mackenzie," she said her teacher replied. 
 
 Frito-Lay, a unit of PepsiCo Inc., ditched the old sack earlier this year after about four years of research. Its replacement: a newfangled bag made from plant material. It's part of a trend among companies trying to boost their green cred to woo customers critical of wasteful or environmentally unfriendly packaging. 
 
 But fiddling with the familiar can be a risky move if companies underestimate the customer's threshold for change. Coca-Cola Co., of course, famously launched a reformulated New Coke in 1985, which flatlined. In 1991, Procter & Gamble Co. changed its green shampoo, Prell, to blue, then undid it after a shampoo-user revolt. 
 
 And just last year, PepsiCo dumped new packaging for its Tropicana orange juice after complaints from juice drinkers about the new look. Just weeks later, Tropicana reverted to its well-known image of an orange pierced by a drinking straw. 
 
 The Sun Chip bag hit store shelves in January and was available nationwide by April. Sales have been in decline, posting year-on-year decreases each month since February (excluding Wal-Mart and some other retailers), according to SymphonyIRI, a Chicago market-research firm. 
 
 A Frito-Lay spokesman said: "There are a lot of potential factors that are playing a role and we are looking at all those things." He accepted packaging could be one of those factors. 
 
 The company has received some complaints about the packaging, he said, but most feedback has been positive. 
 
 The original bags, made from polymers such as polypropylene and polyethylene, weren't recyclable. "They are not designed to degrade," says Brad Rodgers, Frito-Lay's North American manager of sustainable packaging. "Depending on what scientific research you read, it could be more than a 100 years." 
 
 Building a more earth-friendly snack bag was no piece of cake, the company says. The material would need to be able to be printed on while also achieving "barrier performance," says Frito-Lay, which means keeping chips from getting soggy, in lay terms. 
 
 The company settled on a plant-based material, polylactic acid, which fully decomposes in about 14 weeks when placed in a hot, active compost pile. 
 
 To spread its message, Frito-Lay created an elaborate marketing push. One TV commercial uses time-lapse photography to show a Sun Chip bag successfully rotting away. 
 
 So why is the packaging so loud? The new polymers have a higher "glass transition temperature," which is when a polymer goes from a harder, glasslike state to a rubber state. Because the transition to rubberiness happens a bit above room temperature, the bag is "kind of crispy and crunchy," says Mr. Rodgers. 
 
 "The thing is, you feel guilty about complaining since they are doing a good thing for the environment," says Kathy Frederick, a 44-year-old computing consultant at Lehigh University in Bethlehem, Pa. "But you want to snack quietly and you don't want everyone in the house to know you are eating chips." 
 
 Realizing there is no escaping the noise, Frito-Lay featured it in some of its marketing. In stores, the company attached signs to shelves that read: "Yes, the bag is loud, that's what change sounds like." 
 
 Meantime, in the face of the snack-sack attack, Mr. Rodgers is at work trying to de-crunch the bag. "My job as an engineer and scientist is always to constantly improve all our packages," he said. 
 
 Write to Suzanne Vranica at suzanne.vranica@wsj.com 

 Potato Chip Technology That Destroys Your Hearing from heathaplexVISION on Vimeo. 
 
 Sun Chips now comes in a new, 100% compostable bag that completely disintegrates in approximately 14 weeks. Sun Chips are not only better for you than regular chips, but they are better for the environment. There’s only one downside to this new bag technology, it’s TOO FREAKING LOUD! 
 
 Sun Chips now comes in a new, 100% compostable bag that completely disintegrates in approximately 14 weeks. Sun Chips are not only better for you than regular chips, but they are better for the environment. There’s only one downside to this new bag technology, it’s TOO FREAKING LOUD! 
 
 Tags: Hearing, Loudness, Sun Chips, Technology
– Today’s hard-hitting investigative report from the Wall Street Journal: The new Sun Chips bags are loud. Like, really loud. The new bags are biodegradable and compostable (good), but as a result, are also more “crispy and crunchy” (bad). The poor Sun Chips fans who just want to be able to get a midnight snack without waking up the household have compared the sound of the crinkling bag to a “revving motorcycle,” the WSJ reports. One Air Force pilot went so far as to make a video in which he measures the crackling of the bag at 95 decibels and calls it louder than his jet cockpit. A Facebook group called “SORRY BUT I CAN'T HEAR YOU OVER THIS SUN CHIPS BAG” has more than 30,000 fans. What can be done in the face of this madness? A spokesperson says the company is looking into the packaging as a potential reason for declining sales, but for now, signs are going up at store displays: “Yes, the bag is loud, that's what change sounds like.”