(Whenever Superman needed to communicate in space, he always used his super-ventriloquism. Yes, it's a real super-power, and no, I have no idea how the ability to super-throw-your-voice would allow you to speak in a vacuum.)
The crooks are delighted - the soundwave gun may not have killed Superman, but driving him into permanent exile is the next best thing.
But Superman always has a plan: he just finds the nearest white dwarf star and scoops up some neutronium to make a set of homemade earplugs.
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Hmm. You know, this almost seems plausible, given comic-book logic and physics. But imagine trying to duplicate a feat of equal difficulty on a human scale. Let's say you can, with some effort, lug a cinder block in each hand. Now imagine carrying that kind of weight around in your ears. Possible, maybe, with the right leverage - but might it not throw off your balance and posture? And yet Superman seems to have no trouble carrying around two million tons of weight in his ears.
I guess that's why he's Superman, and I'm not.