  By performing numerical simulations of superfluid vortex ring collisions we
make direct quantitative measurements of the sound energy released due to
vortex reconnections. We show that the energy radiated expressed in terms of
the loss of vortex line length is a simple function of the reconnection angle.
In addition, we study the temporal and spatial distribution of the radiation
and show that energy is emitted in the form of a rarefaction pulse. The pulse
evolves into a sound wave with a wavelength of 6-8 healing lengths.
