The lullaby is an underwater soundscape of North Carolina — a recording from a healthy oyster reef’s habitat. It has been shown that wild oyster reefs respond positively to the sounds, or vibrations, of healthy reefs. Metamorphosis takes a certain amount of energy, said Emma Green-Beach, executive director of the Martha’s Vineyard Shellfish Group. Like coral reefs, wild oyster reefs have been degraded over the past few hundred years due to overfishing, pollution and disease. Playing healthy reef sounds isn’t quite a silver bullet, said Mr. Mooney, but it may be a “reef booster shot.”