SIMON and Garfunkel were right - you really can hear the sound of silence.
Philosophers have spent centuries debating whether the noise of nothingness exists, and scientists have finally settled the matter.
Researchers from Johns Hopkins University in Maryland in the United States used a series of auditory illusions to prove that we treat silence in the same way that we treat sounds.
They showed how moments of silence can distort people's perceptions of time and confidently concluded that "nothing is something you can hear".
The team adapted well-trodden auditory illusions to create versions in which the original sounds are replaced by moments of complete silence.
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One illusion convinces participants that a sound is far longer than it actually is, and, in the researcher's adapted illusion, equivalent moments of silence also seemed longer than they actually were.
The authors suggested that the fact that these total quietness-based illusions produced the same results as their sound-based counterparts demonstrates that we hear silence in the same way we hear sounds.
Just as optical illusions trick what people see, auditory illusions can trick what people hear to make periods of time appear longer or shorter than they actually are.
One example is the "one-is-more" illusion, where one long beep seems longer than two short, consecutive beeps - even when the two sequences are the same length.
The research team experimented with 1,000 participants who took reworked, one-is-more-like tests in which the usual sounds were replaced with moments of silence.
The results proved the same, in that participants believed one long moment of silence was longer than two consecutive, short moments of silence.
Study lead author Rui Zhe Goh, a graduate student in philosophy and psychology, said: "We typically think of our sense of hearing as being concerned with sounds.
"But silence, whatever it is, is not a sound - it's the absence of sound.
"Surprisingly, what our work suggests is that nothing is also something you can hear."
Other audio illusions adapted to silence also yielded the same results.
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In one, participants listened to soundscapes simulating the din of busy restaurants, markets and train stations, then listened for periods when all sounds ceased abruptly, creating brief silences.
The idea wasn't simply that these silences made people experience illusions, the researchers said, but that the same illusions scientists thought could only be triggered with sounds worked just as well with silences.
'NOTHING IS SOMETHING YOU CAN HEAR'
Chaz Firestone, an assistant professor of psychological and brain sciences who directs the Johns Hopkins Perception & Mind Laboratory, said the new research was the first to grapple with the sound of silence.
He said: "Philosophers have long debated whether silence is something we can literally perceive, but there hasn't been a scientific study aimed directly at this question.
"Our approach was to ask whether our brains treat silences the way they treat sounds.
"If you can get the same illusions with silences as you get with sounds, then that may be evidence that we literally hear silence after all."
Study co-author Professor Ian Phillips added: "There's at least one thing that we hear that isn't a sound, and that's the silence that happens when sounds go away.
"The kinds of illusions and effects that look like they are unique to the auditory processing of a sound, we also get them with silences, suggesting we really do hear absences of sound too."
The findings, published in the Proceedings of the National Academy of Sciences, establish a new way of studying the perception of absence.
Looking forward, the researchers plan to keep exploring the extent to which people hear silence - including whether we hear silences that are not preceded by sound - and also plan to investigate visual disappearances and other examples of things people can perceive as being absent.
American folk rock duo Simon and Garfunkel released The Sound of Silence, which appeared in the film The Graduate, in 1964.
