When a noise travels faster than the speed of sound and becomes a shock wave.
There’s probably not a person on Earth who didn’t wish for the ability to instantly teleport themselves somewhere else at a given moment. But despite what some science fiction would lead us to believe, even if we had the technology to do it, it wouldn’t exactly be pleasant for the innocent bystanders on the other side. As this episode of It’s Okay To Be Smart explains, the air filling the vacuum where you used to be would collapse with such force, the sound would burst their eardrums and probably make them feel sick to their stomachs.
When we talk about how loud a sound is, what we’re really talking about is how intense the pressure wave created by sound travelling through the air is, says Joe Hanson in the video above. Sound waves are odd because they happen to move outwards from a source in the shape of a sphere. The larger this sphere becomes, and the further away from the source, the less pressure there’ll be at any given point of the sphere.
The smallest sound pressure wave the human ear can perceive is pretty ridiculous – according to the video above, it vibrates our eardrums at less than the width of a single oxygen molecule. Ridiculous.
But what about the loudest sound? Back in 1883, the Island of Krakatoa in the South Pacific erupted into an explosion of fire, molten lava, and gas, which was pummelled into the atmosphere at a force more powerful than the most powerful nuclear weapon ever detonated. This explosion was so loud, it shattered eardrums 65 KILOMETRES away (40 miles).
But this didn’t even hit the upper limit for what a sound can be. You’re gonna have to watch the episode of It’s Okay To Be Smart above to find out what that means, but let’s just say it happens when sound waves move faster than the speed of sound and then become a shock wave.
Watch the video. URL:https://youtu.be/wi_aawsChqA