Can some sounds possibly travel through a vacuum?

Question

What is the possibility that some sounds can travel through a vacuum? There is a new discovery says that it is possible - how can this be possible? Any help would be appreciated.

Answer 1

Can some sounds possibly travel through a vacuum?

There is zero probability of sound being transmitted though space that is empty of all matter, a vacuum. Sound is by its nature transmission of energy on a medium, variation of pressure

Sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids (see Longitudinal and transverse waves, below). The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave.

You ask:

There is a new discovery says that it is possible - how can this be possible?

A similar question was answered here , where the sound is coming from a black hole.

The discovery:

Sound waves 57 octaves lower than middle-C are rumbling away from a supermassive black hole in the Perseus cluster.

Sept. 9, 2003: Astronomers using NASA's Chandra X-ray Observatory have found, for the first time, sound waves from a supermassive black hole. The "note" is the deepest ever detected from any object in our Universe. The tremendous amounts of energy carried by these sound waves may solve a longstanding problem in astrophysics.

If this is the "new discovery" you are asking about, the answer is:

The space around a black hole is not a vacuum, but a very very dilute gas made of leftover particles from the Big Bang and the creation of the black hole itself. It is variation of pressure on the dilute gas that is the sound discovered.

Maybe one should add that sound transcribed on electromagnetic waves can be reproduced any distance away in vacuum with the appropriate electronics at the reception end, so in this sense sound can be transmitted through complete vacuum, since electromagnetic waves do not need a medium.

Answer 2

In an article I read by David Shiga, he describes that a theoretical analysis by Mika Prunnila and Johanna Meltaus of the VTT Technical Research Center suggesting that sound may be able to leap across a vacuum separating two objects made of piezoelectric crystals.

Answer 3

The article by David Shiga being referred to is the one published in the New Scientist magazine: Sound can leap across a vacuum after all (Unfortunately, the content isn't freely accessible and it's actually very expensive to subscribe to the New Scientist!)

On Quora, there are 2 contradicting answers related to a similar question: How does sound energy travel in space and vacuums? but this other question on Quora: Why doesn't sound travel in space? It's not a perfect vacuum. has a large majority of respondents saying that sound requires a medium to propagate and that it can't be heard in a vacuum because there is nothing to compress.

There's more about the experiment carried out by Mika Prunnila and Johanna Meltaus here: Acoustic Phonon Tunneling and Heat Transport due to Evanescent Electric Fields (Scientific publications should be free and open for all!)

My personal understanding is that, in this experiment, the sound wave traveling through a piezoelectric device modifies the lattice structure and thereby generates a varying electric field, which may travel across a vacuum and hit another piezoelectric device. So, in a way, the sound is actually converted to an electromagnetic radiation.

As a conclusion: unless you consider gravity waves, there is no medium to be compressed in a vacuum, therefore sound, which is a longitudinal compression wave, may not propagate through it.