In an electroded metal halide high intensity discharge lamp, the arc is ignited and acoustic resonant oscillations are excited in the fill by a high frequency electrical power supply in order to thoroughly mix the ingredients comprising the fill. Either an amplitude modulated or a non-amplitude-modulated...http://www.google.ca/patents/US4983889?utm_source=gb-gplus-sharePatent US4983889 - Discharge lamp using acoustic resonant oscillations to ensure high efficiency
