A tweet has divided the internet on the bizarre stuff people can do with their bodies, revealing that only a small sector of society can create a 'rumbling' noise in their ears by tensing their muscles.
Twitter user 'Rainmaker 1973', who claims to be a columnist for an Italian science magazine, tweeted that only a "part of the human population can voluntarily control the tensor tympani, a muscle within the ear".
"Contracting this muscle produces vibration and sound. The sound is usually described as a rumbling sound," they added.
According to Wikipedia, the muscle's role is to "damp loud sounds, such as those produced from chewing, shouting, or thunder".
The tweet quickly racked up over 600 shares and nearly 3000 likes, with many people chiming in that they always thought it was something everyone can do.
"Another thing I'm only finding out now that not everybody can do," wrote one person.
"I can do this... I have to close my eyes though," another wrote.
It turns out it's so common there's a sub-Reddit called 'Ear Rumblers Assemble' where those who can conjure the rumbling share their experiences.
Some say it happens accidentally when they shut their eyes tightly, or yawn, but for others they can only do on purpose by flexing the muscles.
"I only learned most people can't do it a year or so ago, after I brought it up to my husband and he looked at me like I was from Mars. I asked Facebook, and someone told me what it was... I'm 36," one person posted.
"All these years and I have only just found out others can do it too!" another posted.
"All I have to do to ear rumble is move the back but of my mouth above my tongue, very hard to explain.
"Here's to the ear rumblers!"