Similar to how light or heat travels, sound travels in waves. What we call “sound” are actually vibrations in the air. In empty space, there is no air, which means that no sound can be produced. Light waves and radio waves do exist in space, however, that is because light does not need air to travel. Since light can travel in space, there is no problem is seeing light, but when it comes to sound a radio must be sent to translate any sound that may be connected with the light waves.
Unless they are in their spacecraft, astronauts in space cannot talk to one another, seeing as there is a lack of air. When astronauts are spacewalking, radios in their helmets allow them to communicate with each other since radio waves are not sound, and can actually exist in space. While some argue that already existing gases in space could propagate sound, just like Earth’s air allows sound to travel, it is highly unlikely that we would be able to hear them. The difference is that gas clouds are much less dense than the Earth’s atmosphere. If sound were to travel through a gas cloud, our ears not being sensitive enough, wouldn’t hear the sound. A large, sensitive microphone could detect the sounds, but our human ear will always hear silence. Space is a vacuum where gases are released into space and expand very quickly while their density decreases. This fact, disproves all movies with explosions in outer space. While an exploding ship would realize gases and sound could technically travel along them, the gases would spread rapidly and lose density quickly, that the sound would deb too faint to hear. Then again, it also depends on distance.
Sound will always need a medium to travel through, whether it be a gas, a liquid or a solid. Sound traveling through a liquid, or even better, a solid, will always be better than sound traveling through gas. The molecules in solids are packed very tightly. Liquids are not packed as tightly as solids, and gases are very loosely. Heat can also be a big component to how fast sound can travel. The hotter the weather is, the more the molecules will bump into each other and the fast sound will travel.
While sound does not travel in outer space, we have ways of interpreting any small vibrations that may occur not loud enough for the human ear to hear.