Beyond the Speed of Sound: The Acoustic Phenomenon That’s Faster Than Light!

esearchers from Middle Tennessee State University have made a startling revelation: sound pulses can travel faster than the speed of light! Yes, you read that right.

By The Frequency Project

Hey sound enthusiasts! 🎵 Ever thought sound could give light a run for its money? Well, scientists have made a groundbreaking discovery that might just make you rethink the limits of sound.

Sound Waves: Not Just Playing by the Rules 🎧

While we’ve always known light to be the ultimate speedster, sound waves are showing they’ve got some tricks up their sleeves too1.

The Science Behind the Speed 🚀

Now, before you start thinking we’ve entered a sci-fi realm, let’s break it down. The researchers didn’t find that the actual sound waves exceeded the speed of light. Instead, it’s the “group velocity” of the sound waves that’s breaking barriers. This “group velocity” is essentially the speed at which the peak of a sound pulse moves through a medium.

The experiment involved sending sound waves through an asymmetric loop filter, which created certain interferences and resonances. Due to these effects, sound pulses traveling through the filter arrived at the exit faster than if they had traveled straight. In some instances, the group velocity was even found to be negative, meaning the peak of the output pulse exited the filter before the input pulse even started! Talk about time travel2.

But, Einstein? 🤔

If you’re scratching your head thinking about Einstein’s theory of relativity, which states nothing can exceed the speed of light, you’re not alone. But here’s the twist: these super-fast sound phenomena don’t actually violate Einstein’s theory or causality. No wave energy in the experiments exceeded the speed of light. The sped-up pulse was a smaller replica of the input pulse, and at all times, the energy of the wave was equal to or less than what it would have been without the filter3.

Real World Implications 🌍

While this might sound (pun intended!) like a quirky lab experiment, the phenomenon could be more common than we think. The interference observed in the experiment is similar to the “comb filtering” effect in architectural acoustics. So, this super-fast sound effect might just be an everyday occurrence that’s gone unnoticed until now4.

Wrapping it Up 🎁

Sound has always been a fascinating realm of study, and discoveries like these push the boundaries of what we know. So, the next time you’re jamming to your favorite tune or listening to the hum of nature, remember: there’s more to sound than meets the ear!

For a deeper dive into this sonic breakthrough, check out the original study here.


  1. Robertson, W., et al. “Sound beyond the speed of light: Measurement of negative group velocity in an acoustic loop filter.” Applied Physics Letters 90, 014102 (2007).

image of 'Mach c'? Scientists observe sound traveling faster than the speed of light

‘Mach c’? Scientists observe sound traveling faster than the speed of light