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.
The Doppler Effect. The Doppler Effect is a phenomenon in which the observed frequency of a source is less or more than the true frequency as a result of either the source or the observer or both moving. It takes it name from Christian Doppler who came up with this idea in 1842.