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Entries found for search: AM

anamorphic /: The camera/projector lens system which squeezes an image, usually originally in a 2:1 aspect ratio) onto film during shooting and "unsqueezes" it during projection. The resulting viewed image has an aspect ratio twice as wide as what was originally recorded on the film, e.g., if the image on the print is 2.2:1, the screen image will be 2.4:1. See also CinemaScope, flat(4), ‘scope.

AM suppression : The ability of an FM tuner or receiver to reject amplitude modulation of the received signal and be sensitive only to frequency modulation. Much of the interference and noise in broadcasting appears as amplitude modulation, so a tuner with good AM suppression will have less distortion and noise than a tuner with poorer suppression. Also called AM rejection.

amp/speaker simulator : A filter circuit that mimics the amplifier and loudspeaker voicing of an electric guitar and amplifier system.

Amplitude Modulation (AM) : The instantaneous amplitude modulation of one signal by another. This results in the formation of sidebands which contain the same information as the original signals, but translated upwards and downwards in frequency. In AM radio transmission, the audio signal is combined with a very high-frequency sine wave, called a carrier, in such a way that the amplitude of the carrier is varied in exact response to the amplitude and frequency of the signal. This is called the amplitude modulation of the carrier. The modulated carrier is transmitted at high power where it is received by radio sets that are tuned to the carrier frequency. The modulated carrier is then demodulated by a process called detection, recovering the original signal. In radio, a circuit that does amplitude modulation is also called a heterodyne.

amplitude errors : See frequency response errors, jitter.

amplitude : The relative strength (amount) of a signal, without regard to its frequency content. Amplitude is measured by determining the amount of fluctuation in air pressure (of a sound), voltage (of an electrical signal), or numerical data (in a digital application). When the signal is in the audio range, amplitude is perceived as loudness. Amplitude is the measurement of how much energy the sound has, i.e., the total change in air pressure during a single cycle of the sound wave. Amplitude, or sound pressure, is measured in a scale called decibels (dB). An increase of 3dB is equal to a doubling of a sound’s pressure. Amplitude can be expressed as either a negative or positive number, depending on the signals being compared. See also magnitude, SPL.

amplifier gain : The amount of amplification that an amplifier provides is called its gain. The gain is a ratio of the input signal level to the output signal level and is simply a number. Commonly expressed in dBindB, one should not express the voltage gain of an amplifier in dBindB unless the input and output impedances are matched as the gain of a typical amplifier is not related to its power output capability. For instance, if an amplifier has a voltage gain of 10, it might be said that it has a gain of 20dB because it actually would raise the power level of a signal by 20dB if the input and output impedances were matched. In practice, however, this is very seldom the case, and the true power gain is usually very much different from what would be predicted by the voltage gain. See impedance matching.

amplifier : An electrical circuit or device designed to increase the current, voltage, or power of an applied signal. An amplifier is an active device and, strictly speaking, should always increase the power of a signal; some amplifiers, such as certain distribution amplifiers, may only reduce the impedance level of the signal for the purpose of driving long lines.

ampere (A) : The unit of measurement for electrical current in coulombs (6.25 x 10^18 electrons) per second. There is one ampere in a circuit that has one ohm resistance when one volt is applied to the circuit. One should not speak of the "flow of current." The current exists; the charge flows. This is analogous to the current in a river, which consists of the flow of water.

AMPEX : A former manufacturer of videotape recorders, analog audio tape recorders, and associated magnetic tape media. For the historic trivia fan, AMPEX is an acronym based on the founder’s name, Alexander M. Poniatoff Excellence.

ambisonics : A system for the reproduction of a three-dimensional sound field, using two or more transmission channels and four or more loudspeakers. See Soundfield microphone.

AMEI : Association of Music Electronics Industries. A group that works with MMA on MIDI standards, among other things.

ambient sound : Sounds such as reverberation, room tone, walla and atmospherics that form a background to the main sound, usually in the context of a film soundtrack of a motion picture, taking place at any given moment. The lack of ambient sound is noticeable because the human hearing system expects it. See also ambient noise.

ambient noise : Ambient sound which is environmental in nature, such as traffic noise coming through walls, heating or air conditioning, or other extraneous sounds which cannot be turned off or removed.

ambience track : An edited roll of magnetic film, or one track of a multitrack tape, assembled by the sound editor in preparation for the final mix of a motion picture or video production, containing the series of room tones or ambient sounds of the various sets and locations in which a scene was shot.

ambience : Ambience refers to the acoustical qualities of a listening space, such as reverberation, echoes, background noise, etc. On most music recordings, some of the ambience is recorded along with the music and are, to a certain extent, reproduced in the listening environment, e.g., an organ in a cathedral. See room tone, walla, NC Curve.

A-DAM : Akai Digital Audio Multitrack. A format developed by Akai in 1987 for recording twelve tracks of digital audio data on a standard Video-8 cassette and which allows the synchronization of multiple decks for 24- or 36-track recording. The tape runs at four times the normal Video-8 speed and gives about 15 minutes sof’ recording time at 44.1kHz.

bantam : See TT connector.

Betacam : A professional analog videotape in Beta format, but at an increased tape speed, which gives picture quality comparable with the 1" C format. Betacam also allows separate recording of the red, green, and blue picture information via its RGB mode for computer use. This capability gives much better control of edge-cuts in special effects. Often called Beta for short.

Betamax : A system used for color videotape recording, developed by Sony for consumer systems. Generally acknowledged to give higher picture quality than VHS.

biamp : Short for biamplification. A two-way crossover network.

Cinerama : A widescreen system comprising three 35mm cameras/projectors running in interlock with 7-track mag film.

combining amplifier : An amplifier, also called a summing amplifier, that combines two or more signals prior to sending them to a single audio bus, signal processor, tape recorder track, or other destination. For example, on a mixer ifthean aux send controls on all channels of a console feed a combining amplifier, whose output can be routed to a reverb system, cue or headphone amp, the monitor amplifier, etc. There are also devices which are active combining amplifiers, called an ACA, as well as passive combining networks,

edit programmer : A computer used to perform on-line edits and auto-assemblies. The video editor enters the EDL, a sequence of SMPTE timecode time codes corresponding to the shots and specific frames to be connected. The edit programmer then controls the video playback and re-recording decks to produce the edited video master tape according to the editor’s instructions. Depending on the sophistication of the specific unit used, the editor may have to perform some special effects manually, on prompts given by the edit programmer. Also called an edit controller.

Registered Parameter Number : (RPN): An extension to MIDI which allows for additional Control Change messages. RPNs have a Control Change number of 100 (LSB) and 101 (MSB). These are defined in the following way:

Unregistered Parameter Numbers (NRPNs) are vendor-defined and may vary among systems. NRPNs have a Control Change number of 98 (LSB) and 99 (MSB).

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