When you send an electrical current through the electromagnet, it becomes magnetized and acts like a natural magnet, with a north pole and a south pole. The electromagnet is surrounded by a permanent natural magnet. In the next section, we'll find out about the clever trick that makes this possible.Ī basic speaker is built around an electromagnet, a metal cylinder with a wire coiled around it. In this system, originally used in the quadraphonic home stereo recordings of the early 1970s, four channels of audio information are encoded into two tracks. In order to allow for four separate audio channels, they developed a special 4-2-4 processing system. When Dolby engineers started working on the new format, they figured out they would only be able to fit two optical tracks in the available space. The real innovation of Dolby Stereo is how so much audio information is squeezed into a small space on the film. (See How Home Theater Works for more information.)
#Dolby 5.1 audio pro
In 1987, Dolby introduced Dolby Pro Logic®, which had an additional channel for a front central speaker. The speakers are set up in the same basic way as in a theater, except the original home Dolby system only had three channels - left speaker, right speaker and rear speaker. The audio channels are encoded as magnetic tracks on video tape or broadcast as a television signal, rather than put down as optical tracks. Dolby Surround reproduces the effect of Dolby Stereo in the theater, but it works a little bit differently. In 1982, Dolby launched Dolby Surround ®, a version of Dolby Stereo for home entertainment systems. The subwoofer channel in both analog and digital surround-sound systems is sometimes called the low frequency effects (LFE) channel. Many moviemakers use the subwoofer to create a powerful rumbling in the theater, shaking the audience when there is an explosion or earthquake on-screen. In later versions of the surround-sound system, theater owners could hook up a subwoofer to handle extremely low-frequency sounds (a crossover unit can separate out these sounds from both audio tracks). Later movies followed the " Star Wars" model, using the surround track to create fantastic effects, as well as fill in background noise to establish a scene's setting.
In the next section, we'll learn a little bit about how surround sound was created and see how it was configured in older theaters.
#Dolby 5.1 audio movie
Sound editors and mixers take a number of different audio recordings - dialogue recorded on the movie set, sound effects recorded in a dubbing studio or created on a computer, a musical score - and decide which audio channel or channels to put them on.
Almost all movie surround soundtracks are created in a mixing studio. There are special microphones that will record surround sound (by picking up sound in three or more directions), but this is not the standard way to produce a surround soundtrack. In this article, we'll use it in this generic sense. While the term "surround sound" technically refers to specific multi-channel systems designed by Dolby Laboratories, it is more commonly used as a generic term for theater and home theater multi-channel sound systems. Surround recordings take this idea a step further, adding more audio channels so sound comes from three or more directions. When you listen to these two channels on separate speakers, it recreates the experience of being present at the event. The simplest two-channel recordings, known as binaural recordings, are produced with two microphones set up at a live event (a concert for example) to take the place of a human's two ears. Two-channel sound is the standard format for home stereo receivers, television and FM radio broadcasts. This isn't entirely accurate, as stereo (or stereophonic) actual refers to a wider range of multi-channel recordings. Two-channel recordings, in which sound is played on speakers on either side of the listener, are often referred to as stereo. Mono means that all the sound is recorded onto one audio track or channel (a single spiraled groove in a record, for example, or a single magnetic track on tape), which is typically played on one speaker. The simplest method, and the one used in the earliest sound movies, is called monaural or simply mono. There are many ways to make and present a sound recording.
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