I want to assure everyone that just because we are overlooking all the fatal parts of being in space without a spacesuit (cold, heat, vacuum, radiation, etc.), we are still going to be scientific up in here.

You are absolutely right that energy can’t be destroyed, even if you’re really mad at it and hit it with a goblin sword. This is a fundamental Law of Physics™. And to review, the reason that sound doesn’t travel in space is because there is no medium with which to transmit it. We can take that one step further, though. Not only does sound not travel through space, there is literally no sound in space. And it doesn’t violate any laws of physics. Promise.

I think what you’re really wondering is “If my vocal cords vibrate, then where does that vibrational energy go?” Well, your vocal cords can’t vibrate in the vacuum of space. Making sound in our throats requires building up air pressure behind our larynx, bringing the vocal folds together like two blades of grass pressed between your thumbs, and then pushing that air upward in order to create a vibration. The oscillating folds of your vocal cords displace air in a repeating pattern, many times per second. Just like when you move your hand through water, it is the displacement of the air by the vocal folds that creates the wave, and the sound is simply the effect of that wave traveling through air. Make sense?

If there’s no air to be displaced, there’s no wave (and no sound). Also, even if you had a lungful of air before you took your space helmet off, you wouldn’t be able to hold the air back from rushing into the vacuum of space. “Woosh” is the sound the last breath in your lungs (doesn’t) make as it is sucked out into the vacuum. No breath control? No vibration.

But what about vibrations that don’t require a lungful of air? What about something like a tuning fork?

Well, a struck tuning fork would vibrate in space. And like the above case, it still wouldn’t make any sound, because no air, etc. Would a tuning fork vibrating in a vacuum vibrate forever? If you let it float away, with no air or other medium to vibrate in, would it still be buzzing a hundred thousand years from now, should aliens find it?

Nope. 

Vibrating objects like tuning forks or space stations struck with large hammers will lose the vibration over time thanks to something called “thermoelastic damping”. A vibration is slowly converted to heat thanks to the atoms in the metal (or whatever’s vibrating) being compressed. And because of the very physics that we mentioned at the start of this question, the vibration dies away, the energy is converted to heat, and Newton is happy!

Of course, don’t try this at home.