# How to study Gravitational Redshift of Sound Waves?

1. Nov 20, 2009

### sunroof

The gravitational shift of a photon in vacuum df/f=gH/c^2 had been confirmed by Pound and Rebca in 1960s. As to sound waves, the result is unclear. A proposal in 2000 was df/f=gH/(340m/s)^2 in air on the surface of the earth.( On the dynamics of mechanical waves and phonons, Journal of Pure and Applied Ultrasonics, volume 22, No.4, 106-110).

On the other hand, the Mach angle sin=340/V (V is the velocity of motion) of supersonics was deduced from a new way (http://arxiv.org/abs/0911.2359 ) which implies the ratio between the energy and mass of a phonon is indeed the square of the speed of mechanical waves. This can be regarded as an indirect evidence to the above conclusion.

Whether there exist other theories or not?

Last edited: Nov 20, 2009