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4:3
Standard television sets aspect ratio. The standard television aspect ratio is four units of measure wide for every three high. |
16:9
A widescreen aspect ratio also called Enhanced Format. 16 units of measure wide per 9 units high. Widescreen format presents images in the same view as the movie theater. |
5.1
An audio format having five full-range channels (usually left front, center, right front, right rear, and left rear) plus a low-frequency effects channel. A 5.1-channel system will typically have six speakers total. Dolby Digital and DTS are both examples of 5.1-channel surround sound formats. |
6.1
An audio format having six full-range channels (the same as in a 5.1-channel system but with the addition of a center back channel) plus a low-frequency effects channel. A 6.1-channel system will typically have seven or eight (if two are used for the center back as recommended by THX) speakers. Dolby Digital Surround EX and DTS-ES are both examples of 6.1-channel formats. |
7.1
An audio format with seven, discrete full-range channels plus a low-frequency effects channel. Some manufacturers of A/V receivers refer to their equipment as 7.1-channels when they include two discrete amplifiers for dual center back speakers. Although this is a good thing in terms of having available amplifier power, in reality no current surround encoding formats provide 7.1 discrete channels of information -- but, hey, there's always tomorrow! |
1080i
A TV picture that is broadcast or shown on a screen using 1080 lines of pixels that are scanned in an interlacing manner in which every other line is scanned/illuminated before the skipped lines are scanned/illuminated. 1080i is the most commonly used HDTV format, and has been adopted by most television broadcast, cable, and satellite outlets as their HDTV broadcast standard. |
1080p
A TV picture that is broadcast or shown on a screen using 1080 lines of pixels that are scanned in a progressive manner in which each line is scanned one after the other, providing the most detailed high definition video image that is currently available to consumers. However, since 1080p is not officially part of the FCC's approved HDTV broadcast standards, it is displayed either as a result of video upscaling through a specially modified DVD player, video scaler, or a Blu-ray Disc Player, in combination with a 1080p input capable video display device (such as a Television or Video Projector) OR by on-board video processing within the Display device itself than can upscale all input sources to 1080p. |
480i
A TV picture that is broadcast or shown on a screen using 480 lines of pixels that are scanned in an interlacing manner in which every other line is scanned/illuminated before the skipped lines are scanned/illuminated. |
480p
A TV picture that is broadcast or shown on a screen using 480 lines of pixels that are scanned in a progressive manner in which each line is scanned one after the other. |
720p
A TV picture that is broadcast or shown on a screen using 720 lines of pixels that are scanned in a progressive manner in which each line is scanned one after the other. |
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A/V Inputs
The connections on any component, such as a TV, receiver or VCR that enable connection to other output devices. The inputs often take the form of RCA jacks. |
A/V Receiver
Also called a Home Theater receiver, sometimes the term "integrated" is also used. Receivers take audio signals from components such as a CD player, tape deck and phonograph, amplify it and output it to the speakers. An A/V receiver is designed to also accept video inputs, such as from a DVD player, cable box and VCR, and output the signal to a television. In most cases, the video signal is not processed but simply passed through to the TV. A/V receivers, in most cases, also have Dolby and DTS decoders to play multi-channel audio, or the “surround-sound” commonly known by most people. |
Absorption
Reduction of acoustical energy usually by converting it into heat via friction using soft, fibrous materials. |
AC3
Audio Codec 3. This was the original name for Dolby Digital. Replaced by marketing mavens when they realized that Dolby's name was not in the title. Some RF modulated, 5.1-encoded laser discs were labeled as AC3. Later versions were labeled as Dolby Digital. |
Acoustic Center
The point in space of the origin of sound. For a sound emitting transducer (e.g., a loudspeaker), the point from which the spherical waves appear to diverge as observed at remote points. (See also acoustic origin.) |
Active
Powered. An active cross-over is electrically powered and divides the line-level signal prior to amplification. An active speaker includes an active crossover and built-in amplifier. |
AM
Amplitude modulated. |
Ambience
In room acoustics, early reflections and reverberation. The audible sense of a room or environment surround a sound source. |
Ampere
The unit of measurement for electrical current in coulombs per second |
Amplifier
A component that increases the gain or level of an audio signal. |
Amplitude
A parameter of sound related to the extent of oscillation of a vibrating body, of sound pressure, or of an analog voltage. |
Analog
When a signal is continuously variable, it is analog. When a signal is broken into units that are rounded to discrete values, it is digital. Analog signals contain "all of the data" but it is prone to interference and degradation. It is not possible to catch and remove all of the interference from an analog signal, so the quality declines as it travels to your TV. With a digital signal, certain values are expected. When a value is received that is not within the expected range, it can be filtered or adjusted. This ability to detect and filter or repair a digital signal makes it possible to deliver a signal to your TV that is as good as when it left the studio. |
Anamorphic
Process that horizontally condenses (squeezes) a 16:9 image into a 4:3 space, preserving 25 percent more vertical resolution than letterboxing into the 4:3 space. For the signal to appear with correct geometry, the display must either horizontally expand or vertically squish the image. Used on about two or three promotional laser discs and many DVDs. Also called Enhanced for Widescreen or Enhanced for 16:9. |
Antenna
A device for transmitting or receiving signals. The size and shape of antennas are determined primarily by the frequency of the signal they are designed to receive. A high gain antenna is highly focused, whereas a low gain antenna receives or transmits over a wide angle. |
Artifact
Any imperfection in a video image resulting from digital processing such as interlacing, up or down-conversion of the signal or conversion from a native to non-native format and vice-versa. |
Aspect Ratio
A television's aspect ratio is the relationship of the horizontal dimension (the width of the screen) to the vertical dimension (the height). It can be expressed as a ratio of whole numbers (4:3 or 16:9) or a ratio using fractional numbers for the width compared to the height of one unit (1.33:1 or 1.78:1). Images with wider aspect ratios tend to engage more of your peripheral vision and draw you deeper into the theatrical experience. |
ATSC
Advanced Television Systems Committee. Government-directed committee that developed our digital television transmission system. |
Attenuate
The lessening of sound signal level due to divergence, absorption, reflection, refraction, diffraction, etc., typically expressed in decibels. |
Audio outputs
An audio output is a connection (most often an RCA jack) on a device, such as a TV, that can be connected to a stereo or home theater system. A fixed output means the stereo is used to control the volume. A variable output means that the TV and the stereo can each control the volume. |
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Balanced Input
A connection with three conductors: two identical signal conductors that are 180 degrees out of phase with each other, and one ground. This type of connection is very resistant to line noise. |
Bandpass
A two-part filter that cuts both higher and lower frequencies around a center band. A bandpass enclosure cuts high frequencies by acoustic cancellation and low frequencies by natural physical limitations on bass response. |
Brightness
For video, the overall light level of the entire image. A brightness control makes an image brighter; however, when it is combined with a contrast, or white level control, the brightness control is best used to define the black level of the image (see Black Level). For audio, something referred to as bright has too much treble or high-frequency sound. |
Bandwidth
In audio, the range of frequencies a device operates within. In video, the range of frequencies passed from the input to the output. |
Bass
Low frequencies; those below approximately 200 Hz. |
Boost
To increase, make louder or brighter; opposite of attenuate. |
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Cathode Ray Tube
(CRT) Analog display device that generates an image on a layer of phosphors that are driven by an electron gun. |
Coaxial
1) A speaker typically with one driver in the middle of, and on the same axis as, another driver. 2) An audio or video cable with a single center pin that acts as the hot lead and an outer shield that acts as a ground. |
Crossover
A device, either passive (as in a speaker) or active (as in a processor) that directs particular frequencies to particular drivers or speakers. |
Composite Video
A signal that contains both chrominance and luminance on the same 75-ohm cable. Used in nearly all consumer video devices. Chrominance is carried in a 3.58-mHz sideband and filtered out by the TV's notch or comb filter. Poor filtering can result in dot crawl, hanging dots, or other image artifacts. |
Component Video
A signal that's recorded or transmitted in its separate components. Typically refers to Y/Pb/Pr, which consists of three 75-ohm channels: one for luminance information, and two for color. Compared with an S-video signal, a Y/Pb/Pr signal carries more color detail. HDTV, DVD, and DBS are component video sources, though most DBS material is transcoded to component from composite signals. |
Codec
Mathematical algorithms used to compress large data signals into small spaces with minimal perceived loss of information. |
Contrast
Relative difference between the brightest and darkest parts of an image. A contrast control adjusts the peak white level of a display device. |
Chord
The simultaneous sounding of a group of notes, usually three or more. In Western music, chords of three notes consisting of the first, third and fifth degrees of a scale are called triads. Major triads consist of intervals of a major third (four semitones) and perfect fifth (seven semitones) with respect to a reference pitch (the root). The third is minor (three semitones) in a minor triad. The third is major and the fifth is augmented (eight semitones) in an augmented triad. The third is minor and the fifth is diminished (six semitones) in a diminished triad. When the notes of a chord are played in ascending or descending succession, the melodic figure is called an arpeggio. |
Cut
To reduce, lower; opposite of boost. |
Cascading Crossovers
Two crossovers used in series on the same signal in the same frequency range causing greater attenuation of the out-of-band signal. For example, using the crossover in a receiver's bass management setting and the one in a subwoofer simultaneously will create an exaggerated loss of signal. |
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Digital Video Recorder (DVR)
A Digital Video Recorder is like a VCR, but with a hard drive and without the hassles of videotapes or timers.Think "tape-less" VCR and more. Digital Video Recorders record shows digitally and save them to a hard drive. All recorded programs are listed on your TV screen for playback in any order. |
Dolby B
A noise-reduction system that increases the level of high frequencies during recording and decreases them during playback. |
DVD-R
A recordable DVD format similar to CD-R in that it is a write-once medium. Backed by Pioneer, Panasonic, Toshiba, and others. |
DVD+R
A recordable DVD format similar to CD-R in that it is a write-once medium. Backed by Sony, Philips, Yamaha, HP, and others. |
DVD-RW
A recordable DVD format similar to CD-RW in that it is re-recordable medium. Backed by Pioneer, Panasonic, Toshiba, and others. |
DVD+RW
A recordable DVD format similar to CD-RW in that it is re-recordable medium. Backed by Sony, Philips, Yamaha, HP, and others. |
DVD-RAM
A recordable DVD format similar to DVD-RW in that it is a re-writeable format. Unlike DVD-RW it is capable of being written to and erased over 100,000 times. Backed by Hitachi, Panasonic, Toshiba, and others. |
Driver
A speaker without an enclosure; also refers to the active element of a speaker system that creates compressions and rarefactions in the air. |
Decibel (dB)
A unit of the intensity of sound. The decibel (abbreviated dB) is a relational measure, expressing the relative intensity of the described sound to a reference sound. The decibel is a logarithmic measure, specifically 10 times the logarithm of the ratio of two voltages, currents or sound pressures. A difference of 20 dB between two sounds means that the more intense one has 10 times the amplitude (100 times the power) of the softer. A single decibel is commonly thought to be the smallest change in sound pressure level that the trained human ear can detect. |
Diffusor
Acoustical treatment device that preserves sound energy by reflecting it evenly in multiple directions, as opposed to a flat surface, which reflects a majority of the sound energy in one direction. |
Dolby Digital
An encoding system that digitally compresses up to 5.1 discrete channels of audio (left front, center, right front, left surround, right surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV broadcast, or other form of digital media. When RF-modulated, it was included on some laser discs, which requires an RF-demodulator before the signal can be decoded. Five channels are full-range; the .1 channel is a band-limited LFE track. A Dolby Digital processor (found in most new receivers, preamps, and some DVD players) can decode this signal back into the 5.1 separate channels. Most films since 1992's Batman Returns have been recorded in a 5.1 digital format, though a number of films before that had 6-channel analog tracks that have been remastered into 5.1. |
Dolby Pro Logic II
An enhanced version of Pro Logic. Adds improved decoding for two-channel, non-encoded soundtracks and music. |
DTS ES
An enhanced version of the 5.1 DTS system. Like Dolby's Surround EX, a sixth channel is added. In some cases (DTS ES Discrete), the sixth channel is discrete. Software is backwards-compatible with 5.1 systems, but requires an ES or 6.1 processor to obtain additional benefit. Neo:6 is a subset of DTS ES that creates 6.1 from material with fewer original channels. |
Dolby Pro Logic
An enhancement of the Dolby Surround decoding process. Pro Logic decoders derive left, center, right, and a mono surround channel from two-channel Dolby Surround–encoded material via matrix techniques. |
Dolby EX
An enhancement to Dolby Digital that adds a surround back channel to 5.1 soundtracks. The sixth channel is matrixed from the left and right surround channels. Often referred to as 6.1. Sometimes referred to as 7.1 if the system uses two surround back speakers, even though both speakers reproduce the same signal. Software is backwards-compatible with 5.1 systems, but requires an EX or 6.1 processor to obtain additional benefit. |
Dolby C
An improvement on Dolby B that provides about twice as much noise reduction. |
Dolby Digital Surround EX
Co-developed by Dolby and THX, Surround EX adds a center back channel to the five main channels of audio in Dolby Digital-sometimes referred to as 6.1 channels, the .1 being the LF (Low Frequency) effect channel sent to the subwoofer. |
DSP
Digital Signal Processing. Manipulating an audio signal digitally to create various possible effects at the output. Often refers to artificially generated surround effects derived from and applied to two-channel sources. |
DTV
Digital Television. Umbrella term used for the ATSC system that will eventually replace our NTSC system in 2006. HDTV is a subset of the DTV system. While the FCC does not recognize specific scan rates in the adopted DTV system, typically accepted rates include 480i, 480p, 720p, and 1080i. |
DTS
Digital Theater Systems. A digital sound recording format, originally developed for theatrical film soundtracks, starting with Jurassic Park. Records 5.1 discrete channels of audio onto a handful of laser discs, CDs, and DVDs. Requires a player with DTS output connected to a DTS processor. |
DVD-A
Digital Versatile Disc-Audio. Enhanced audio format with up to six channels of high-resolution, 24-bit/96-kHz audio encoded onto a DVD, usually using MLP lossless encoding. Requires a DVD-A player and a controller with 6-channel inputs (or a proprietary digital link) for full compatibility. |
D-VHS
Digital VHS. Digital signals recorded onto magnetic tape. Greater capacity than typical VHS; can record compressed HDTV signals. See D-Theater |
DVI
Digital Visual Interface. Connection standard developed by Intel for connecting computers to digital monitors such as flat panels and DLP projectors. A consumer electronics version, not necessarily compatible with the PC version, is used as a connection standard for HDTV tuners and displays. Transmits an uncompressed digital signal to the display. The latter version uses HDCP copy protection to prevent unauthorized copying. See also HDMI. |
DBS
Direct Broadcast Satellite. Term that replaced DSS to describe small-dish, digital satellite systems such as DirecTV and Dish Network. |
DNR
Dynamic Noise Reduction. A signal-processing circuit that attempts to reduce the level of high-frequency noise. Unlike Dolby NR, DNR doesn't require preprocessing during recording. |
Diffusion
In audio, the scattering of sound waves, reducing the sense of localization. In video, the scattering of light waves, reducing hot spotting, as in a diffusion screen. |
DLP
Invented by Texas Instruments, the Digital Light Processing(TM) technology refers to a sophisticated combination of a light source, a projection lens, and a Digital Micromirror Device (known as the DMD chip) that contains over a million tiny, hinged mirrors used to reflect an image on to a screen. On this chip, each mirror corresponds to one pixel in the projected image. |
Damping
Of or pertaining to the control of vibration by electrical or mechanical means. |
DVD
Officially known as the Digital Video Disc, though marketers unofficially refer to it as the Digital Versatile Disc. DVD uses a 5-inch disc with anywhere from 4.5 Gb (single layer, single-sided) to 17 Gb storage capacity (double-layer, double sided). It uses MPEG2 compression to encode 720:480p resolution, full-motion video and Dolby Digital to encode 5.1 channels of discrete audio. The disc can also contain PCM, DTS, and MPEG audio soundtracks and numerous other features. An audio-only version, DVD-A uses MLP to encode six channels of 24-bit/96-kHz audio. |
Delay
The time difference between a sonic event and its perception at the listening position (sound traveling through space is delayed according to the distance it travels). People perceive spaciousness by the delay between the arrival of direct and reflected sound (larger spaces cause longer delays). |
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Echo
A sound wave which has been reflected or otherwise returned with sufficient magnitude and delay (typically >90 milliseconds) to be perceived as distinct from that directly transmitted. |
EDTV Monitor
An Enhanced Definition TV without an included DTV tuner. |
EQ
Equalization or Equalizer. |
EDTV
Short for Enhanced Definition TV. This type of television must be able to display images at scanning rates higher than 480p but not as good as HDTV. It must also include a DTV tuner capable of receiving all 18 DTV broadcast formats. |
Enclosure
The container of air that surrounds the rear of a speaker driver. |
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Filter
A device that can change the relative amplitudes and phases of the frequency components in the spectrum of a signal. A high-pass filter attenuates low frequencies and lets the high ones pass through. A low-pass filter does the opposite. |
Full-Range
A speaker designed to reproduce the full range (20 Hz to 20 kHz) of audio frequencies. |
Fricative
A speech sound produced by frication, that is, by forcing air through a constriction in the vocal tract. Examples are "s" and "f." |
Front Projection TV
A type of television that projects an image onto a screen or wall in front of the projector. |
Frame
An image on a TV screen using all of the lines. In an interlace system, two fields (1/60th of a second) combine to make one frame (one 1/30th of a second). |
FM
Frequency Modulated. |
Fiber Optic Cable
Glass, plastic, or hybrid fiber cable that transmits digital signals as light pulses. |
FireWire
See IEEE 1394. |
Frequency
The number of cycles (vibrations) per second. In audio, audible frequencies commonly range from 20 to 20,000 cycles per second (Hz). In video, frequency is used to define the image resolution. Low-frequency video images depict large objects or images. Higher frequencies depict smaller objects (finer details). |
Feedback
The transmission of current or voltage from the output of a device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it's in phase with the input and negative when it's out of phase. |
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Gain
Increase in level or amplitude. |
Gray Scale
The ability for a video display to reproduce a neutral image color with a given input at various levels of intensity. |
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Home Theater in a Box
A complete home theater system in one box (or at least sold together as a package). Consists of five or more speakers, a subwoofer, and a receiver. May also include a DVD player. |
Hi-Fi Stereo
Feature found on VCRs that records or plays back stereo soundtracks with improved fidelity compared to using the linear stereo tracks. |
HDMI
HDTV connection format using a DVI interface that transfers uncompressed digital video with HDCP copy protection and multichannel audio. |
Hz
Hertz or cycles per second. Something that repeats a cycle once each second moves at a rate of 1 Hz. |
HDCP
High-Bandwidth Digital Content Protection. Created by Intel, HDCP is used with HDTV signals over DVI and HDMI connections and on D-Theater D-VHS recordings to prevent unauthorized duplication of copyright material. |
HDTV
High-Definition Television. The high-resolution subset of our DTV system. The FCC has no official definition for HDTV. The ATSC defines HDTV as a 16:9 image with twice the horizontal and vertical resolution of our existing system, accompanied by 5.1 channels of Dolby Digital audio. The CEA defines HDTV as an image with 720 progressive or 1080 interlaced active (top to bottom) scan lines. 1280:720p and 1920:1080i are typically accepted as high-definition scan rates. |
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Integrated Amplifier
A combination preamp and amplifier. |
Impedance
A measure of the impediment to the flow of alternating current, measured in ohms at a given frequency. Larger numbers mean higher resistance to current flow. |
Interconnects
Any cable or wire running between two pieces of A/V equipment. For example, RCA terminated cables connecting pre/pros and amps. |
IEEE 1394
Networking standard for PCs. Combined with 5C copy protection, is used as a two-way connection to transfer the MPEG-compressed digital bitstreams between consumer electronics items, including HDTV tuners and displays, D-VHS recorders, DVD players, and DBS receivers. Also called FireWire, iLink, … |
iLink
See IEEE 1394. |
Imaging
The ability to localize the individual sound sources in three-dimensional space. |
Intensity
The name given to the physical energy with which a sound is present. It contrasts with "loudness," which is the perceptual experience approximately correlated with that physical intensity. |
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Keystone
A form of video image distortion in which the top of the picture is wider than the bottom, or the left is taller than the right, or vice versa. The image is shaped like a trapezoid rather than a rectangle. |
kHz
Kilohertz or one thousand Hz. |
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Low Pass
A filter that lets low frequencies go through but doesn't let high frequencies go through. Same as high cut. |
Letterbox
Format used widely on laser disc and many DVDs to fit wide-aspect-ratio movies (1.85:1 and 2.35:1, for example) into a smaller frame, such as the 1.78:1 area of an anamorphic DVD or the 1.33:1 area of a laser disc or video tape. The image is shrunk to fit the screen, leaving blank space on the top and bottom. This process sacrifices some vertical detail that must be used to record the black bars. |
LCD
Liquid Crystal Display. A display that consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between. Voltage is applied to certain areas, causing the crystal to turn dark. A light source behind the panel transmits through transparent crystals and is mostly blocked by dark crystals. |
LCOS
Liquid Crystal on Silicon |
LFE
Low Frequency Effects track. The .1 channel of a Dolby Digital, DTS, or SDDS soundtrack. The LFE is strictly low-frequency information (20 to 120 Hz, with 115 dB of dynamic range) that's added to the soundtrack for extra effect. This track does not inherently contain all the bass of the soundtrack. |
LNB
Low-Noise Blocker. The receiving end of a satellite dish. |
Laser Disc
Now-defunct 12-inch disc format with excellent analog, FM-recorded video image, and either analog or CD-quality PCM-encoded audio. Later discs used one of the analog channels to record an RF-modulated Dolby Digital/AC3 soundtrack and/or used the PCM tracks to encoded a DTS soundtrack. |
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Multizone
A term that refers to the ability to have different sound or pictures in more than one room of your home at the same time. |
Multiple-Rate Encoding
Instead of locking encoding at a certain constant data rate, it allows the codec to choose whatever rate is best for that portion of the recording. Usually reduces file size with proportionally less loss in quality. |
MHz
Megahertz, or 1 million Hz. |
Mono
Monophonic sound. One channel. |
MP3
The name of the file extension and also the name of the type of file for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (more specifically, the redundant and irrelevant parts of a sound signal. The stuff the human ear doesn't hear anyway). Because MP3 files are small, they can easily be transferred across the Internet. |
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Noise
An unwanted portion of a signal such as hiss, hum, whine, static, or buzzing. |
Negative Gain Screen
Material that reflects less light than a reference material. Often used for DLP and LCD projection systems. |
NTSC
National Television Standards Committee. Government-directed committee that established the U.S. color TV standard in 1953. Also known, sarcastically, as Never Twice the Same Color or Never The Same Color due to the inherent difficulty in achieving proper color calibration. |
Networking
The linking of a number of devices, such as computers, workstations, printers, and AV gear into a network (system) for the purpose of sharing resources. |
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Ohm
A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance. |
Optical Digital Cable
Fiber optic cable that transfers digital audio signals as light pulses. |
Octave
The difference between two frequencies where one is twice the other. For example, 200 Hz is an octave higher than 100 Hz. 400 Hz is one octave higher than 200 hz. |
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Pulse Code Modulation
(PCM) a way to convert sound or analog information to binary information (0s and 1s) by taking samples of the sound and record the resulting number as binary information. Used on all CDs, DVD-Audio, and just about every other digital audio format. It can sometimes be found on DVD-Video. |
Pre/Pro
A combination preamp and surround processor. |
Preamplifier
A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers. |
Parallax
A major clue to the perception of depth in vision, parallax arises from the relative motions of near and far objects that is produced when the viewer moves his or her head up and down or from side to side. See also stereopsis. |
Power Output
A measure, usually in watts, of how much energy is modulated by a component. |
Piezo
A type of speaker driver that creates sound when a quartz crystal receives electrical energy. |
Processors
Anything that processes an incoming signal in some way. Surround processors, for example, can decode a Dolby Digital signal to send to an amp so you can hear it. |
Pre Outs
Connectors that provide a line-level output of the internal preamp or surround processor. |
Pixel
Contraction of picture element. The smallest element of data in a video image. |
Projection System
Display that projects image onto a screen. |
Progressive Scanning
Each frame of a video image is scanned complete, from top to bottom, not interlaced. For example, 480p means that each image frame is made of 480 horizontal lines drawn vertically. Computer images are all progressively scanned. Requires more bandwidth (twice as much vertical information) and a faster horizontal scan frequency than interlaced images of the same resolution. |
Parametric
Equalizer with adjust-able parameters, such as center frequency and bandwidth (Q), as well as amplitude. |
Plasma
Flat-panel display technology that ignites small pockets of gas to light phosphors. |
Passive
Not active. A passive crossover uses no external power and results in insertion loss. A passive speaker is one without internal amplification. |
PVR
Personal Video Recorder. Marketing term for Video HDRs. |
Power Amp
See Amplifier. |
Pitch
The auditory attribute on the basis of which tones may be ordered on a musical scale. Two aspects of the notion of pitch can be distinguished in music: one related to the frequency (or fundamental frequency) of a sound (measured in Hz) which is called pitch height, and the other related to its place in a musical scale which is called pitch chroma. Pitch height varies directly with frequency over the range of audible frequencies. This "dimension" of pitch corresponds to the sensation of "high" and "low." Pitch chroma, on the other hand, embodies the perceptual phenomenon of octave equivalence, by which two sounds separated by an octave (and thus relatively distant in terms of pitch height) are nonetheless perceived as being somehow equivalent. This equivalence is demonstrated by the fact that almost all scale systems in the world in which the notes are named assign the same names to notes that are roughly separated by an octave, i.e., the labeling system cycles at every octave. Thus pitch chroma is organized in a circular fashion, with octave-equivalent pitches considered to have the same chroma. Chroma perception is limited to the frequency range of musical pitch (50-4000Hz). |
Phase
The phase is the particular point in a wave that is passing a position in space at a certain instant of time. Phase is measured in units of degrees, with 360 degrees representing one complete cycle of the wave. If two tones have the same period and are occurring at the same time, the temporal lag of one with respect to the other can be described in terms of phase. If two waves are out of phase by 180 degrees, the later one is lagging by one-half a period. |
Polarity
The positive or negative direction of an electrical, acoustical or magnetic force. Two identical signals in opposite polarity are 180 degrees apart at all frequencies. Polarity is not frequency dependent. |
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Receiver
Any component that receives, or tunes, broadcast signals, be it NTSC, HDTV, DBS, or AM/FM radio. Typically refers to the single component that includes a preamp, surround processor, multichannel amplifier, and AM/FM tuner. |
Rear-Projection Television
Display that projects an image on the backside of a screen material, usually after having been reflected off of a mirror. |
RF
Radio Frequency. Television signals are modulated onto RF signals and are then demodulated by your television's tuner. VCRs and DBS receivers often include channel 3 or 4 modulators, allowing the output signal to be tuned by the television on those channels. Also, laser discs used an RF signal for modulating Dolby Digital 5.1 soundtracks on some movies. This requires an RF demodulator (usually referred to as an AC3-RF demodulator) before or in the surround processor to decode the signal. |
RCA Jacks
Receptacles for coaxial cables carrying line-level audio signals. Also called phono-type connectors. |
RGB
Red, Green, Blue. Can refer to an unprocessed video signal or the color points of a display device. Together these three colors make up every color seen on a display device. |
RMS
Root Mean Square or the square root of the arithmetic mean (average) of the square's set of values. A reasonably accurate method of describing an amplifier's power output. |
Resonant Frequency
The frequency at which any system vibrates naturally when excited by a stimulus. A tuning fork, for example, resonates at a specific frequency when struck. |
Reverberation
The reflections of sound within a closed space. |
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Source
A component from which the system's signals originate. DVD player, AM/FM tuners, and VCRs are sources. |
Speaker
A component that converts electrical energy into acoustical energy. |
Spectrum
A description of the frequency content of a sound waveform, usually presented as a graph with frequency on the abscissa (x axis) and amplitude on the ordinate (y axis). A pure tone would have a single vertical line at the appropriate frequency with a height indicating its amplitude. A complex sound (see complex tone) would have several such lines, indicating the multiple components. Drawing a curve through the tops of the lines would describe the spectral envelope. A spectrogram is another representation of a spectrum in which the time component is reintroduced: time is represented on the abscissa, frequency on the ordinate, and amplitude is coded as the darkness of the trace at a given frequency and time. In an auditory neural spectrogram, instead of a continuous signal, the probability of occurrence of nerve spikes at a given moment in time is represented. The frequency axis is replaced by a frequency-specific auditory nerve channel (see basilar membrane). A third type of spectral representation called a time-frequency perspective plot is drawn in three dimensions, with time along the x axis, amplitude along the y axis, and frequency along the z axis. |
Structured Wiring
A method of wiring a home for audio, video, telephone, and computer using a centrally located, often modular panel. |
Scale, musical
A set of pitches (or notes) arranged with certain intervals among them within the span of an octave (see also pitch). The scale pattern generally repeats in each octave. Each note constitutes a degree of the scale. Each diatonic scale consists of intervals between adjacent notes that are either minor or major seconds (one or two semitones, respectively). The different arrangements of major and minor seconds yield different modes. The two most important modes in Western tonal music are the major and minor modes. The chromatic scale contains all twelve semitone steps within an octave. Another kind of scale which does not fall within the tonal system but which was used extensively in the music of Debussy and Ravel is the whole-tone scale, which has only six notes, all separated by whole tones. Intonation (or tuning system) refers to the exact tuning of the notes of a given scale system. The most widely used tuning system in Western music is the equal-tempered system in which all intervals can be expressed as integer multiples of a standardized semitone. This system was brought to Europe from China and adopted during the 17th century. |
Subwoofer
A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz. |
Square wave
A square wave is one in which there are only two values of the displacement of the wave from the neutral position, a positive displacement and an equally large negative displacement. The wave moves instantaneously form one state to the other and remains equally long in each state. Its spectrum contains odd harmonics only, whose intensities are inversely proportional to the harmonic number. |
Sound
Energy that transmitted by pressure waves in air or other materials and is the objective cause of the sensation of hearing. Longitudinal vibrations in a medium in the frequency range 20 Hz to 20 kHz. |
Sinusoidal
Having the shape of a sine wave. |
Sampling Frequency
How often a digital sample is taken of an analog wave. The more samples taken, the more accurate the recording will be. You need to sample at a minimum of twice the highest frequency you want to capture. For example, the 44.1-kilohertz sampling rate of a CD cannot record sounds higher than 22.05 kilohertz. |
Speed of sound
In air, approximately 1130 feet per second at 20 degrees Centigrade. |
SDTV
Standard Definition Television. Lower resolution subset of the ATSC's DTV system. 480i is typically accepted as an SD signal. Digital broadcasters can offer multiple sub-programs at SDTV quality, as opposed to one or two HD programs. Digital satellite and digital cable often refer to the majority of their programs as SDTV, somewhat erroneously, as neither system has anything to do with DTV, though both, technically, consist of a digital 480i signal. |
SACD
Super Audio CD. Enhanced audio format with up to six channels of high-resolution audio encoded using DSD. Requires an SACD player. Multichannel also requires a controller with six-channel analog or proprietary digital inputs for full playback. |
S-VHS
Super VHS. Enhancement to regular VHS that offers improved luminance resolution. (400 lines or so.) |
Soundstage
The area between two speakers that appears to the listener to be occupied by sonic images. Like a real stage, a soundstage should have width, depth, and height. |
Scan Lines
The lines drawn by an electron gun in a CRT system to make up the picture. Drawn horizontally, from left to right, starting at the top left and working to the bottom right. |
Signal-to-noise ratio (S/N)
The ratio in decibels between signal and noise. An audio component with a high signal-to-noise ratio has relatively little background noise accompanying the signal; a component with a low signal-to-noise ratio is noisy. |
Sine wave
The simplest form of periodic wave motion, expressed by the equation y = sin x, where x is degrees and y is voltage or sound pressure level. All other forms can be created by adding (mixing) a number of sine waves. The wave form of a "pure tone" is a sine wave. |
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Transmission Line
A (sub)woofer cabinet design where the driver is mounted at one end of a tube with the same diameter as the radiating area of the driver and a length of 1/4 wavelength of the 3dB down frequency. This "tube" may or may not be round and may be folded to decrease the size of the cabinet. |
Tweeter
A speaker driver designed to reproduce high frequencies; usually those over approximately 5,000 to 10,000 Hz. |
Timbre
Also referred to as sound quality or sound color. The classic negative definition of timbre is: the perceptual attribute of sound that allows a listener to distinguish among sounds that are otherwise equivalent with respect to pitch, loudness, and subjective duration. Contemporary research has begun to decompose the attribute into several perceptual dimensions of a temporal, spectral, or spectro-temporal nature. |
Transducer
Any device that converts one form of energy into another form of energy, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound (mechanical impulses), a microphone converts sound into electrical impulses, a solar cell converts light into electricity, etc. |
THX Select
Certification program for speakers and receivers that assures a base level of quality and performance when played in a room that's between 2,000 and 3,000 cubic feet. |
THX Ultra
Certification program for speakers, receivers, and amplifiers that assures a base level of quality and performance when played in a room that's greater than 3,000 cubic feet. |
THX Ultra 2
The newest certification from THX, THX Ultra 2 requires amplification for seven channels, boundary compensation for subwoofers, and stricter requirements for amplifiers and speakers than THX Ultra. Dipole speakers are used for the side surround channels. Monopole speakers are used for the surround back channel and are placed next to each other. The Ultra 2 processor accommodates both 5.1 EX/ES soundtracks, as well as multichannel audio recordings by directing ambient sounds to the dipole speakers and discrete effects/sounds to the back channels. |
Tempo
The speed of occurrence of the beats for a given metric structure. In a musical score, the tempo is specified in terms of the number of metric units per minute, for example, quarter-note = 60, in which the time value of each quarter-note is 1 second. The inverse of tempo, the time between beats, is called the beat period. |
THX
THX is the trade name of Lucasfilm Limited's high-fidelity sound reproduction system for theatrical movie theaters, screening rooms, home theaters, and car audio systems. THX was developed by George Lucas's company in 1983 to ensure that the soundtrack for the third Star Wars film would be accurately reproduced in the best venues.The THX system is not a recording technology, and it does not specify a sound recording format; all digital and all analog sound formats can be "shown in THX." THX is mainly a quality assurance system. |
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Universal Remote
Remote that has the commands of numerous brands stored into memory and can control several different devices simultaneously. |
Upconvert
Typically used to describe the process by which a DTV tuner or HDTV creates additional scanning lines for an image that starts with fewer scanning lines. This is sometimes referred to as line doubling. |
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Video Cassette Recorder
Device that records audio and video electrical signals onto magnetic tape (aka videotape recorder). |
VCR
See Video Cassette Recorder. |
Volt
The unit of electrical potential, or difference in electrical pressure, expressing the difference between two electrical charges. |
VCR Plus
VCR feature that, once programmed, allows the user to input the TV guide code for a given program into the VCR, which then automatically sets itself to record that program. |
VHS
Vertical Helical Scan (or as JCV calls it, "Video Home System"). Widely used method of recording audio and video electrical signals onto magnetic tape. |
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Watt
A unit of power or energy. One horsepower is equal to 745.7 watts. |
WMA
Windows Media Audio. An audio compression format similar to MP3, but with digital rights management (copy protection and usage restrictions) built-in by Microsoft. |
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Y/Pb/Pr
See component video. |
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Zone
One or more rooms powered by one or more amplifiers, which are all fed by one source. A home can be divided into multiple zones, which can play multiple sources, even though several rooms (say, the kitchen, dining room, and living room) all play the same source. |
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