SOME people can hear a strange rumbling noise in their ears when they tense their muscles.
A Twitter science enthusiast who goes by Massimo went viral after tweeting about a muscle in your lugs that can create a "roar" noise.
To create the sound, which comes from inside your ear, you have to contract the muscle – but most people can't do this.
Simply screw up your face really tightly, including your eyes, and see if you can hear a low, thunder-like rumble.
Massimo : "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."
The phenomenon has been known about since the 19th Century.
It's thought that the muscle in question, the tensor tympani, dampens out loud noises such as sound of your own chewing or the clap of thunder.
When tensed, the muscle changes the shape of the eardrum to dampen vibrations and protect the ear.
Some people can do this manually, creating a rumbling sound.
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How to make the 'roar' noise
- Try scrunching up all of your face muscles and closing your eyes
- This action can also tense a muscle in your inner ear, creating a rumbling sound
- Only some people can do it, so if you can't hear anything, you may be out of luck
- You can also replicate the sound by clenching another muscle near your ear
- For instance, try scrunching up a fist and squeezing it tight while holding it to your ear
"To me it sounds like when there’s a big thunderstorm," one Twitter user wrote in response to Massimo's post.
"The thunder is just lowly rolling around in the sky forever with only tiny flashes of lightning that don’t leave the clouds."
Others expressed surprise that not everyone could create the strange sound.
"I can do this! Woo! Didn’t know it was an uncommon thing. I have to close my eyes though," one user wrote.
Another said: "I didn't know what that was, but I've always been able to do that. Cool, thanks for this post! I've learned something new."
Other people didn't have quite as much luck producing the sound.
One tweeted: "I'm not one of these people and I feel like what it must be for colorblind people being privy to the discussion among normochromats."
The discussion sparks memories of "the dress", which drove a global online debate in 2015.
It involved a photo of a dress posted online which some people saw as gold and white while others saw it as black and blue.
The dispute became so famous that it has since been used by neuroscientists in research over colour perception.
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