Residents near Paignton Zoo in Devon are possibly being kept awake at night by giraffes humming.
Neighbours have complained about the sound for over a year and thought it could be a boiler in the giraffe zoo.
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To be good neighbours, the zoo vowed to check their equipment for the low-level sound but did not find anything.
According to the Torquay Herald Express, new research suggests the giraffes themselves could be to blame.
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Experts say the animals can communicate in infrasound at frequencies too low for humans to hear.
According to the Daily Mirror, scientists say giraffes have a larynx but it is not clear how it is used.
The humming may be giraffes communicating with each other.
Angela Stoger of the University of Vienna, told New Scientist magazine: "I was fascinated, because these signals have a very interesting sound and have a complex acoustic structure."
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