Prostate-specific antigen (PSA) is a substance produced by the prostate gland. Elevated PSA levels may indicate prostate cancer, a noncancerous condition such as prostatitis, or an enlarged prostate.
Dolby Digital, formerly known as AC-3, is a digital audio coding technique that reduces the amount of data needed to produce high quality sound. Dolby Digital takes advantage of how the human ear processes sound.
Doppler effect. The Doppler effect is defined as a noticeable change in the frequency of sound, light or water waves as the source and the observer move. An example of the Doppler effect is that the frequency of the sound increases as the source moves closer to the observer.