Imagine biting into a juicy red apple and not hearing the satisfying crunch. Or pouring champagne and seeing the effervescence rise enticingly in the glass but not hearing its fizzy sound. A growing body of research is proving that what we hear when eating and drinking not only affects how much we enjoy the experience, it can change our perception of how things taste.

Sound “is the forgotten flavor sense,’’ says experimental psychologist Charles Spence, on the phone from the University of Oxford’s Crossmodal Research Laboratory in England. Spence, who heads the lab, is studying how the senses work together to create our perceptions of food and drink. He is among a pioneering group of scientists and chefs who are reshaping how we think about flavor.

Flavor, according to this new way of thinking, is the result of the integration of information from all five senses. “Everybody focuses on the taste and smell,’’ says Debra Zellner, professor of psychology at Montclair State University, but visual, auditory, and tactile cues have a huge impact, she says.

This sensory interplay appears in seemingly all aspects of eating and drinking. Zellner, who collaborates on flavor research with the Monell Chemical Senses Center in Philadelphia, has demonstrated correspondences between shape and flavor, for example, finding that milk chocolate is associated with soft, cloud-like shapes, and more bitter dark chocolate with the sharp and angular. Eating yogurt with heavier cutlery improves its flavor ratings and makes it seem more expensive, according to Spence’s research, and seeing red food elicits expectations of sweet taste, while green evokes sour.

Spence’s foray into how sound influences flavor came in 2004 with the “sonic chip’’ experiment. In the first study to demonstrate that the sounds food makes change how we perceive what we eat, Spence placed headphones over the ears of a group of volunteers who then bit into a series of Pringles potato chips, rating crispness and freshness. Spence recorded their chomping sounds, adjusted the volume and frequency, and piped them back through the headphones as the volunteers ate.

Though the chips were all the same — the uniformity of Pringles makes them an ideal testing material — volunteers ranked them as crisper and fresher when the crunching sounds were louder or the higher-frequency sounds were intensified. When the sound and frequencies were lower, the chips were rated as softer and stale.

Sounds in the environment also change our perception of food, says Spence. In a series of studies looking at how music corresponds with flavor, Spence discovered that pitch can alter the taste and aroma of food. In one such study, volunteers ranked the bittersweet candy cinder toffee as more bitter while listening to the low pitch of brass music, and sweeter when listening to the high pitch of a tinkling piano. Spence calls this ability to modulate flavor with music “sonic seasoning.’’

Changing the flavor of food with sound may seem far-fetched, but we routinely make these kinds of connections to help us navigate the steady bombardment of sensory input we are faced with every day. “Our brains are picking up correlations in the environment all the time,’’ says Spence. Making compatible associations helps us to better predict the world. “We’re not born thinking that red is sweet, but we learn that as fruits ripen, they go from green and sour to red and ripe and sweet,’’ says Spence. “When we learn that, we know which tree to go to for ripe fruit.’’

Chefs with an experimental bent are using these sound associations to micro-engineer dining experiences. Heston Blumenthal is chef and proprietor of the Michelin-starred restaurant The Fat Duck, in Bray, England, and a longtime advocate of multisensory-focused fare. In 2007, after working with Spence to demonstrate that oysters taste better when the eater listens to ocean sounds, he put his signature dish, Sounds of the Sea, on the menu. Made to look like the sea — fish and shellfish sit among seaweed and edible “sand’’ — it is served with an iPod playing the sounds of waves gently breaking and seagulls cawing overhead. These kinds of well-matched sound associations draw upon prior experiences of diners, evoking nostalgia and bringing focus to the food, says Spence.

Sound in the environment can also have a discordant impact on flavor. Obnoxiously clamorous restaurants are on the rise — the result of loud music and modern decor that does away with sound-absorbing tablecloths, cushions, and curtains. That racket may be changing the way diners experience the food on their plates. “Loud noise masks some tastes and enhances others,’’ says Spence. “It distorts your tasting experience.’’

Food marketers are reveling in the goldmine found in multisensory flavor research. Global companies like Unilever, Procter & Gamble, Kellogg’s, and Nestlé are carefully considering everything from the tactile qualities of their products to how the shape and sound of packaging set expectations for what’s inside. Spence’s sonic seasonings inspired British Airways to create playlists that enhance the flavors of in-flight meals made blander by loud airplane noise. Krug Champagne has created a cap of Limoges porcelain to amplify the popping bubbles of its Grande Cuvée.

This psychological approach to food is also being put to use to help people. Spence is working with Ferran Adrià’s Alícia Foundation using music in a hospital outside Barcelona to improve eating experiences for children whose appetites have diminished due to chemotherapy. Zellner and the Monell Chemical Senses Center are working to optimize environmental sensory cues to encourage healthy eating in a Philadelphia school lunch program. Multisensory associations may facilitate reductions in salt and sugar, making food healthier without sacrificing flavor.

“By picking up these surprising connections that we all share, you can actually design things that are meaningful,’’ says Spence. “There is a lot more information there than we ever realized.’’

Valerie Ryan can be reached at valerie.ryan.j@gmail.com.