It’s the sound that usually occurs when you shut your eyes tightly or flex your jaw muscles in a certain way. It sounds like a low rumbling or a 747 passing by. One young reader sent us this question, and wanted us to explore this little life mystery. She asks, “What’s that sound you hear when you shut your eyes tightly? Is it harmful?”

Blame A Muscle

The sound you are hearing is produced by the tensor tympani muscle in your ear. It’s main function is to dampen sounds produced by your own chewing.

It is possible to contract this muscle voluntarily which produces vibrations and thus the sound. Slow twitch muscle fibers produce 10 to 30 contractions per second. The fast twitch muscle fibers produce 30 to 70 contractions per second. These contractions produce the sound you hear.

To see an example of this effect, just tighten your fist as tight as you can and hold it in that tensed position. The tremors and vibrations you will see are the exact same thing that’s happening in your ear when you clench down on your jaw real hard.

If you place that tightened up fist near your ear, you might be able to hear the same sound if you listen very carefully in a quiet room. The sound from your fist’s muscles will sound like a low rumbling noise. Some people can voluntarily produce this effect by contracting their tensor tympani muscle. The sound can also be heard when the eyes are closed tight, or when the neck/jaw muscles are highly tensed – like when yawning deeply.

Flexing this muscle or holding the sound for extended lengths of time is not harmful or damaging to the ear in any way. The only way a person could get permanent, sensorineural hearing loss from the contraction of the middle ear muscles is if they both came from a common cause, like a tumor.

Ear Popping

Some people are also able to pop their ears at will, without having to hold their nose and blow. This isn’t because of the tensor tympani though, it’s thanks to a different muscle called the Salpingopharyngeus muscle. It’s primary function is to raise the pharynx and larynx during swallowing. It is also responsible for the equalization of pressure between the auditory canal and the pharynx.

Bonus Facts:

Last year, Lasha Patraya of Georgia set a world record for the strongest ears by pulling an 8 ton truck 70 feet with his ears.

While Caucasians and Africans are more likely to have wetter, darker earwax, Asians and American Indians have flaky, dry, earwax thanks to the ATP-binding cassette C11 gene.

References:

Vibrations and sounds from evoked muscle twitches., Electromyogr Clin Neurophysiol. 1992 Jan-Feb;32(1-2):35-40.

Information on Tinnitus Hyperacusis