Nicola Twilley in the New Yorker on an experiment to see how sound affects our sense of what is fresh.

…Over the next few weeks, Spence invited twenty research subjects to his basement lab and sat them in front of a microphone in a soundproof booth. There they were handed a pair of headphones and instructed to bite, one by one, into nearly two hundred Pringles original-flavor chips. After a single crunch, each subject spat out the chip and gave it a rating: crisper or less crisp, fresh or less fresh. The subjects could hear each crunch as it looped from the mike into the headphones. But, without letting the participants know, Spence funnelled the crunching noises through an amplifier and an equalizer, allowing him to boost or muffle particular frequencies or the over-all volume. About an hour later, released from the booth, each subject was asked whether he or she thought all the chips were the same.

The chips were identical, of course, but nearly all the volunteers reported that they were different—that some had come from cans that had been sitting open awhile and others were fresh. When Spence analyzed his results, he saw that the Pringles that made a louder, higher-pitched crunch were perceived to be a full fifteen per cent fresher than the softer-sounding chips. The experiment was the first to successfully demonstrate that food could be made to taste different through the addition or subtraction of sound alone. Spence published his results in the Journal of Sensory Studies, in 2004. The paper, written with a post-doc, Massimiliano Zampini, was titled “The Role of Auditory Cues in Modulating the Perceived Crispness and Staleness of Potato Chips.”