Would you hear a gravitational wave, if its amplitude and frequency were suitable?

Question

If there was a source of a continuous gravitational wave at (say) 50hz, and amplitude of say a micrometer (a typical sound wave displacement, I think), and you were nearby (standing happily on a planet in an atmosphere), with your ear pointing to the source, would you hear it?

It seems to me that since the gravitational wave is reducing and increasing the distance between points in the atmosphere right at your eardrum, surely the density and pressure of the air there is likewise increasing and decreasing, so you might expect to hear it. What I can't "intuit" is whether you would actually hear it due to the fact that you yourself are also being distorted.

My tentative conclusion is that you would hear it. At any given time, there appears to be a pressure differential across your eardrum due to this distortion in space pressurising the materials - so ... deflection?

(note: I know that in the recent LIGO announcement they talked about "hearing" the waves, but this is something completely different: an electro-acoustic rendition of the waveform. I'm asking about direct physical sensing.)

Answer 1

The frequency of the recent experiment was in the audible range. The amplitude was off by unspeakable orders of magnitude. But yes, you would hear it (even in vacuum, if you were to survive).

Yes, the GW are transverse (quadrupolar). But they do move things (they cause change in distances, that's actually how they detected them: the length of the 4km tube at LIGO changed; earlier experiments actually planned to detect the "sound" of a vibrating metal cylinder, but they weren't sensitive enough). An eardrum and the bones around them are a complex instrument and whatever direction the strain is applied, it would surely induce a vibrational motion that would produce vibration of the eardrum, even if not in the way you imagine (compare to sound, where there is direct pressure to the eardrum -- GW are more profound and make the eardrum itself directly deform and vibrate). If you were close enough to a cataclismic cosmic event, you would hear it across the emptiness of the space. Both directly (as induced vibrations in our bones), and through creaking of the structures around us.

It's interesting to note that generally the same instrument that was used more than a century ago to prove that velocity of the "aether" is impossible to detect (disproving the notion of an elastic medium permeating the universe) was now used to prove acceleration of the "aether" (so to speak) can and was measured.

Answer 2

Lets look at the problem on a quantum mechanical level. Sound is generated by vibrating atoms in a solid transferring their energy to the air, and the energy moves in sound waves and reaches our ears or instruments. This happens with the exchange of electromagnetic interactions, at a complex level, but still photons and scatterings are involved.

A gravitational wave is composed of gravitons, but the coupling constant is very very much smaller than the electromagnetic one. There is no transfer of energy to the lattices of the solid that could change the pressure and generate sound waves. It passes as is, without losing energy, through our eardrums too because of the extremely weak coupling with matter.

Answer 3

From wikipedia:

The effects of a passing gravitational wave can be visualized by imagining a perfectly flat region of spacetime with a group of motionless test particles lying in a plane (e.g., the surface of a computer screen). As a gravitational wave passes through the particles along a line perpendicular to the plane of the particles (i.e. following the observer's line of vision into the screen), the particles will follow the distortion in spacetime, oscillating in a "cruciform" manner, as shown in the animations. The area enclosed by the test particles does not change and there is no motion along the direction of propagation.

https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:GravitationalWave_PlusPolarization.gif

Answer 4

If you would hear it, it would be a matter of the stretching-and-compressing motion due to the GW themselves causing a reaction on your hearing organs (those beyond your eardrums). The air itself interferes minimally: it is deformed behind your eardrums in exactly the same way as it is outside (this does not depend on the specific nature of the waves, be it transverse or longitudinal), hence there is no pressure difference which can cause your eardrum to vibrate. Also, the wavelength of the GW ($\frac{3.10^8}{50}m=6.10^6 m$) is way too long to cause significant pressure gradients in the atmosphere and therefore cause "secondary" sound.

EDIT: solid (perhaps some liquid) bodies may start to chime significantly though, especially those who have fundamental frequencies at 50 Hz, that could be a significant "tertiary source".

Answer 5

I don't see how you could hear gravity waves even if they were of the appropriate frequency and amplitude. Hearing depends on the motion of hairs in the vestibular system, specifically the relative motion between the hair and its attachment in the cochlea. If a gravitational wave were to pass, all parts of the organ would move together and the hairs would not transmit a signal to the nervous system. Therefore you could not hear a gravitational wave. That's the way I see it.