So where do the myths about the brown noise come from? The internet has helped rumours spread faster than ever before, and satirical articles are regularly shared as fact on Facebook, but Leventhall believes the idea of the brown noise first originated from
a spoof article in
New Scientist from over 40 years ago.
"It's the earliest reference to a sound causing diarrhoea that I've come across," he says. "I remember when I first saw the article after it was published in 1974; I didn't quite cotton on that it was a spoof. It's very subtle and quite convincing."
The article refers to the opening ceremony of the Great Exhibition in Victorian England, where thousands of people gathered. It claims that during the national anthem a horn let off the supposed "brown note", causing the crowd to immediately start wetting themselves and uncontrollably shitting everywhere. Reading like a 19th century slapstick comedy, it's not hard to see how it captured so many imaginations.
Here's what we know about the "brown note": it's supposedly in the infrasound area, somewhere below 20 hertz – which is beyond the lower limit of what the average human can detect. Within this infrasound region, the frequency of 7 hertz has always been shrouded in mystery because of supposedly harmful effects.
One day, back in the 1970s, Dr Leventhall read a French scientific paper that suggested subjecting yourself to this frequency could cause instant death. "I was so mad about this that I sat in my sound chamber to listen to 7 hertz myself," he says. "It was turned up to 145 decibels, which was a very high level and clearly audible. Nothing happened to me and I was still alive at the end of it."