An international collaboration between physicists and music researchers has uncovered the way to determine if a watermelon is ripe: pat it and listen to the sound it makes.
Nigerian music researcher Stephen Onwubiko, who is working with watermelon sellers in the markets in the Igbo region of the country, says the sound begins deep and becomes lighter as the fruit ripens. It is a pattern that also features in Nigerian music.
To quantify the sounds Onwubiko has teamed up with Traci Nielsen, an acoustic physicist at Brigham Young University in the US, as well as music researcher Andrea Calilhanna from the University of Sydney in Australia, who is taking a mathematical approach to music theory.
The team proposes that Nigerians are intuitively attuned to the percussive sounds of watermelons because drumming features heavily in their music.
“The sounds of ripe and unripe watermelons are heard in traditional music,” Neilsen suggests. “An African drum pattern is made from the same two sounds.”
Onwubiko is a classically trained vocalist and made the connection between sounds in the market place and that of the Igba, a cylindrical drum about 70 centimetres long.
In their abstract, he and his colleagues say “the application of the Nigerian drum beat-pattern, pitch and intonation is an efficient procedure for ripeness detection of watermelon.
“Depending on how the pitches are lowered or accented, the melon ripeness is detected.”
The team reports a success rate of 60% in detecting ripeness. They now hope to extend the technique to cover the sound of spoiled watermelons, too.
The researchers are exploring the connection between the measurable acoustic experience and the listeners’ perception, a field known as psychoacoustics.
Onwubiko suggests most Nigerians are not explicitly aware of the relationship of ripeness to sound.
“Most people don’t have much idea about the noises around them or how they affect them,” he says.
“Everyday experiences, even decision making, are influenced by the sounds around us.”
Phil Dooley is an Australian freelance writer, presenter, musician and videomaker. He has a PhD in laser physics, has been a science communicator for the world's largest fusion experiment JET and has performed in science shows and festivals from Adelaide to Glasgow. Under the banner of Phil Up On Science he runs science pub nights around the country and a YouTube channel.
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