The Doppler effect explains changes in the length of light waves or sound waves as they move toward you or away from you.

VOA: special.2009.04.29

"Some of these inventors have been designers of the human genome sequencer, incredible technologies around focusing sound in the same way have been able to focus light with lasers, health technologies like the stair-climbing wheelchair and a portable dialysis machine,".

VOA: standard.2009.12.18

"Let's Shoot" "Light em all up" "Come on fire" (SHOOTING SOUND) In the incident, (SHOOTING SOUND) Wikileaks,the group that posted the video, has identified two of the men as a Reuters news photographer and his driver.

VOA: standard.2010.04.06