The science of sound: What is it about the crunch that keeps snackers dipping in for more?

Eating is a deeply sensory experience and consumers often prize taste, aroma, appearance and texture more so than factors like health and sustainability.

There’s also a growing understanding of the importance of the sound that snacks when eaten and its impact on it perception of quality.

A large body of research delves into the effect that food sound salience – the sound that a food makes during mastication – has on consumption. In fact, researchers believe increased attention to the ‘forgotten’ flavor sense could help consumers avoid overconsumption, a phenomenon is known as ‘auditory-gustatory synesthesia’.

Also coined the Crunch Effect, results found the group subjected to the loudest background noises to cancel out the sounds they made while eating ate four pretzels versus the 2.75 pretzel by those in a quiet environment.

This shows that increased attention to the sound the food makes while being consumed could help decrease consumption,​​ according to a 2016 study published in Food Quality and Preference. Conversely, that showed people will eat more if they cannot hear their own chewing.

“Sound is typically labeled as the forgotten food sense, but if people are more focused on the sound the food makes, it could reduce consumption,” said coauthor Ryan Elder, then assistant profession of marketing at BYU’s Marriot School of Management.

The kHz of crispy, crunchy and crackly​​

Crispy foods (lettuce, potato chips) typically produce high-frequency sounds (above 5 kHz) when eaten, while crunchy foods (peanuts) make sounds at a much lower range (1-2 kHz). Crackly foods (dry biscuits) generate low pitched sounds with a high level of bone conduction*.

Researchers also believe the crunch keeps things interesting, whereas quiet foods don’t provide enough stimulation and the eating experience could ‘become boring more quickly’, according to Prof William E. Lee, who was a food sensory researcher at Procter & Gamble before joining the University of South Florida as associate professor of chemical and biomedical engineering.

His 1990 analysis of food crushing sound during mastication found a crisp product creates higher-pitched sounds.​ ​Using a signal analyzer, he measured the sound generated by a series of 10 consecutive chews on  potato and tortilla chips and found that the fresh samples were louder and emitted higher-frequency sounds than their stale counterparts.

He also found that noisy snackers took more pleasure from the experience, while participants who wore headphones to cancel out the noise ate fewer chips.

Important lesson for marketersPic: GettyImages/WeAreSounds can be used in digital marketing campaigns to engage viewers and stimulate their appetite and TV commercials often emphasize ‘the crunch’ to highlight appeal.

The past decade, in particular, has seen an explosion in the use of background noise, music and specially designed soundscapes to enhance the tasting experience. A 2016 study published in Multisensory Flavor Perception found noise will bias our choices and consumption behavior,​​ enhancing our sensitivity to things like crunchiness and umami, but also supressing our ability to taste things like sweetness.

Conversely, “noise is a source of enjoyment,” said Prof Lee, noting “people will move snack food around the mouth to maximize noise.”

Kids, for example, typically crunch in such a way that seems like ‘they’re throwing noise at each other.”

Auditory cues also keep us craving more, which is why it’s so easy to mindlessly finish off a full-sized bag of Lay’s in front of the TV.

More importantly, consumers associate sound with freshness: a loud crunch is often associated with freshness and quality, while a lackluster sound may be perceived as stale or inferior.

By selectively manipulating the frequency and amplitude of the sound feedback produced when eating a potato chip, researchers have been able to demonstrate a link between sound and perceptions of overall product quality.

A 2003 study published in the Journal of Sensory Studies asked participants to bite into potato chips with their front teeth and rate their crispness or freshness using a computer-based visual analog scale. Results found the potato chips were perceived as being both crispier and fresher – whether they were or not – when either the overall sound level was increased,​​ or when the high frequency sounds (2 kHz−20 kHz) were selectively amplified.

The science behind ‘snap, crackle and pop’Pic: GettyImages/Petia BabbiiSonic words, too, can impact a product’s healthfulness.

Slurp, chomp, munch, snap and plop​ ​are onomatopoeic words that mimic the sounds we hear when eating and thus play into food sound salience, according to a 2021 study published in Food Quality and Preference.

Japanese people, in particular, are more sensitive to different degrees of crispness than North Americans. Another 2021 study – published in the journal Foods – investigated the association between the perceived crispness and palatability of five types of Japanese rice crackers known as ‘kakinotane’​ ​and found onomatopoeias had a greater influence on describing the nuances of food texture than physiological data.

Mimetic words imitate sounds or other sensory experiences and as texture is a sensory property, onomatopoeias can enrich the description of a sensory experience and have a significant influence on gustation.

Crunchy foods are also perceived as harder to eat. For example, potato chip crispness will typically disappear after four or five bites but a tortilla chip is still going strong after 10 bites.

“The longer you use your teeth, the crunchier a product is considered,” said Prof Lee.

“Crispness is sensed in two places. One is in the mouth, by nerve endings including those of the teeth, which create a sharp, sudden, complete break, like the shattering of glass. The other place is the ear. Auditory information is important in assessing a food and just by listening, you can tell if a chip is fresh or stale.

“If the food shows up in the middle of the mouth and the person is using their tongue for compression, that means the product is doughy. With a salty snack, we want to maximize teeth time and minimize tongue time.”

The study of chewing sounds involves a lot more than just the crispiness, crunchy or freshness of a product and the consumer’s perception. It’s a science that involves knowing how the characteristics of the jaw, teeth and soft tissues in the mouth influence the perceived sounds, specifically the bone-conducted sound travelling through the teeth and jaws to the ear*. Then there’s the contribution of air and bone conduction, the number of sound bursts in a bite or chew, the frequency and pressure level and … it gets very complex and scientific.

Suffice to say, the sound of snacking plays a critical role in the overall consumer experience, affecting perception, satisfaction and brand loyalty. It’s a key element in product development, marketing and sensory evaluation and is an essential consideration for snack brands.

Studies:The crunch effect: Food sound salience as a consumption monitoring cue​​

Authors: Ryan S Elder, Gina S Mohr

Food Quality and Preference 2016, 16(39-46); doi.org/10.1016/j.foodqual.2016.02.015

Spectral composition of eating sounds generated by crispy, crunchy and crackly foods​​

Author: C Dacremont

Journal of Texture Studies (1995) 26(1); doi.org/10.1111/j.1745-4603.1995.tb00782.x

Analysis of food crushing sounds during mastication: total sound level studies​​

Authors: WE Lee III, MA Schwitzer, GM Morgan, DC Shepherd

Journal of Texture Studies (1999) 21(2); doi.org/10.1111/j.1745-4603.1990.tb00473.xCitations: 34

Sound: The Forgotten Flavor Sense​​

Editors: Betina Piqueras-Fiszman, Charles Spence

Multisensory Flavor Perception (2016) 81-105; doi.org/10.1016/B978-0-08-100350-3.00005-5

The role of auditory cues in modulating the perceived crispness and staleness of potato chips​​

Authors: Massimiliano Zampini, Charles Spend

February 2005Journal of Sensory Studies (2005) 19(5) 347-363, doi:10.1111/j.1745-459x.2004.080403.x

Figurative Language in Snack Advertising Slogan​​

Authors: Hosana S. Juanda, A. Supriadi

International Journal of Linguistics, Literature and Translation (2022), 5(12); doi.org/10.32996/ijllt.2022.5.12.15

Crispness, the Key for the Palatability of “Kakinotane”: A Sensory Study with Onomatopoeic Words​​

Authors: Atsuhiro Saita, Kosuke Yamamoto, Alexander Raevskiy, et al

Foods 2021, 10(8), 1724; doi.org/10.3390/foods10081724