Select the first letter of the word from the list above to jump to appropriate section
of the glossary.
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- Kbps (sometimes kb/s)
Kilobits per second. -
- kHz
Kilohertz, or thousands of cycles per second. See also Hz.-
- Kell factor
A psychovisual phenomenon that determines how much the eye can resolve on a TV
screen.
- LCD
Liquid Crystal Display. Instead of cathode ray tube (CRT) displays or CRT projection
tubes, some television sets employ the LCD, which is cooler running, lighter in weight,
and smaller in size. Some very small sets have direct-view displays. A few others are
front-projection models that focus light through several LCD panels, with the resultant
image projected to an external screen. See also CRT;
Direct-view television set; Projection television set.-
- LED
Light Emitting Diode. Often used as an indicator on A/V components-
- LEDE
Live-End-Dead-End room. A room designed to attenuate speaker reflections from adjacent
walls, while highlighting the more delayed, scattered reflections from the far end, behind
the listeners. This keeps the recorded signals from being strongly modified by the front
of the listening room and allows the longer delays from the rear to place room-generated
ambience where it belongs. An LEDE room will be heavily padded at the speaker end and
lined with diffusing panels at the other end. The absorptive characteristics of this room
may result in recordings that are overly bright when played back on wide-dispersion
speaker systems located in typical, somewhat more reflective, home-listening rooms.-
- Late reflections
In room acoustics, the sounds that arrive at the listening position after being reflected
from multiple room surfaces. They are the aural clues to the size of the listening space.
In DSP, they are the electrically delayed signals that a home or studio processor creates
to simulate larger room spaces.-
- Learning remote
A remote control that is designed to learn commands from a variety of other (dedicated)
controls, simplifying user control of multiple components.-
- Letterboxing
Video reproduction of a film that places the entire, uncropped picture on the TV
screen-eliminating the pan-and-scan problems that result when a wide format is cropped to
fit a 4:3-ratio (or even, in the case of extremely wide originals, a 16:9-ratio) screen.
The term letterbox is supposed to have been derived by someone's impression of the view
looking out through the mail slot in their door or local mailbox. It describes a view that
is wide but not very tall. Letterbox is not a format, just a phrase that describes the
visual appearance of the piccture on the screen. See also Matting;
Pan and scan.-
- LP
Long Play. In VCR parlance, the middle recording and playback speed available on some
units. In audio, the short term for the analog, long-play, 33 1/3 rpm, vinyl disc.-
- LSB
Least Significant Bit.-
- LV
LaserVideo. This is the earliest laser-read videodisc system; sometimes called the analog
videodisc.-
- Line doubling
See IDTV.-
- Line level
Low-voltage output signals available at the shielded (RCA, XLR) connections of
preamplifiers, CD players, tape recorders, etc., designed to interface with the line-level
inputs of amplifiers, subwoofers, tape inputs, etc. See also Speaker level.-
- Line-source loudspeaker
A line source is a tall, vertically oriented, narrow driver or line of drivers. Because of
this design, the "driver" will behave like a very large source over the vertical
dimension and like a smaller one over the horizontal dimension. When very tall, the
resultant erratic vertical dispersion and phase cancellations will affect performance in
both the direct and reverberant fields.-
- Linear audio track
The monophonic analog sound track that runs down one side of a videotape. Far inferior in
sound quality to what can be obtained with hi-fi videotape, this is what you will hear if
you plug your VCR (even a hi-fi model) directly into the RF input of a TV set.-
- Linear stereo tracks
These are the non-hi-fl stereo tracks that are available on some prerecorded video-tapes.
They usually employ Dolby Noise Reduction to improve the S/N ratio that is
sacrificed when going from a mono linear audio design to stereo, but they are still far
inferior to the stereo tracks that are standard on any hi-fi-audio-equipped video
recorder. This feature has fallen into disuse but may be found on some used models.-
- Liquid-cooled speaker
See Ferrofluid.-
- Liquid-cooled tube
These are found on CRT-type projection television sets and involve a liquid solution
hermetically sealed between the projection tubes and the lens assembly. The coolant
prolongs the life of the tubes and keeps heat expansion from - distorting the picture.
-
- Listening distance
In home audio, the subjective distance of the listener from the performers on a recording.
The distance can be somewhat altered by careful use of the volume control, but the
recorded sense of space around the instruments and the depth of the sound stage that
result from good minimalist microphone techniques will also play a large part in
determining it.-
- Lossy compression
See Data reduction-
- Loudness compensation
A circuit available on many preamplifiers, integrated amplifiers, and receivers that
attempts to compensate for the loss in low-frequency hearing sensitivity at lower volume
control settings. While simplified switched versions usually are crudely effective at best
and certainly less workable than simple bass tone controls, some of the more
sophisticated, continuous-control versions may work well-although still no better than the
bass controls.-
- Low-pass filter
Within an audio crossover network, the electronic or passive circuitry that allows the low
frequencies to go to a speaker system or amplifier. See also High-pass filter.-
- Luminance
The brightness component of a television signal. See also Chrominance.
- Mbps (sometimes mb/s)
Megabits per second-
- MD
See MiniDisc.-
- MOL
Maximum Output Level.-
- MOSFET
Metal-Oxide-Semiconductor-Field-Effect Transistor. A special, high-peak-current output
transistor used in some power amplifiers.-
- MPEG
Motion Pictures Experts Group. A group that meets under the auspices of the International
Standards Organization in order to generate standards for digital-video and video-audio
data compression/reduction.-
- MSB
Most Significant Bit. The first bit in a binary number. In 16-bit digital-audio playback
systems, it contributes 32,000 times more to the output signal than the 16th (least
significant) bit. Thus, errors in MSB circuitry occurring at very low levels can cause
audible distortion and nonlinearities.-
- MTS
Multichannel TV Sound. The standard stereophonic audio reception and noise-reduction
process used in all true stereo television receivers not using satellite or digital
decoders.-
- Macrovision
A jamming signal encoded into most prerecorded videotapes that makes it difficult to do
tape-to-tape copies-
- Masking
Under ordinary conditions, the process by which the threshold of hearing of one sound is
raised by the presence of another. In both digital video and digital audio, a technique
that allows a system to delete superfluous (inaudible or invisible) artifacts from a data
stream by means of data reduction or data compression, enabling the system to transmit or
store wide-bandwidth information within a much smaller bandwidth. Four notable uses of
masking involve Dolby AC-3 Digital Surround Sound, MPEG video, DCC cassettes, and the
MiniDisc. See also Data reduction.-
- Matrixing
In audio, the electrical mixing of two or more channels of sound down to one or more new
ones. The latter can later be "dematrixed" back to the original number. With
two-channel stereo, this will involve both left-plus-right (derived center) and
left-minus-right (extracted ambience) processing. Dematrixing can also be applied to
two-channel stereophonic signals that were not consciously matrixed from multiple
originals, with variable results. While used in FM-signal transmissions and processes to
receive stereo audio signals, its most notable use is in surround-sound processors. See
also Dolby Surround; Hafler circuit; Extraction processors.-
- Matting
The application of a mask to a film or video program to remove information from the top
and/or bottom of a picture. Used extensively in both theater presentations and video
letterboxing. A hard matte is applied to the camera during the filming or
videotaping process and, like anamorphic manipulation, delivers a true wide-screen image.
A soft matte is a postproduction process that is done digitally when a film is
transferred to videodisc or by means of projection gates in a theater.-
- Microphone
An electroacoustic device that turns the acoustic signals that come in contact with it
into electrical signals for recording. Its behavior is just the opposite of that of a
loudspeaker.-
- Midbass
The part of the bass frequency range between roughly 100 and 300 Hz.-
- Midrange
The middle range of the audible spectrum, running anywhere from 300 to 500 Hz on up to 3
or 4 kHz, a total of four octaves or more. The speaker component that handles this area is
called the midrange driver.-
- MiniDisc (MD)
Sony's new data-reduced, small-disc, digital format.-
- Minimalist technique
The use of very few microphones, combined with very little editing, to achieve a natural
sound on an audio recording, particularly with classical or jazz music. Also called purist
technique.-
- Mixing console
The piece of equipment that recording engineers use to edit the material they recorded or
are in the process of recording.-
- Monaural
See Monophonic.-
- Monitor: audio
With regard to recording, this refers to the listening the recording engineer does while
"recording" and editing a program (usually music). With regard to audio
playback, it refers to the speaker systems used in the monitoring and mixing room, which
may be commercial models but can also be models designed for consumer use that are often
better than the commercial models.-
- Monitor: video
Refers to TV sets without a tuner, which thereby require connection to a video source of
some kind to produce a picture. However, many monitors designed for home use have both
monitoring connections and a tuner.-
- Monophonic
A recording or sound system that has only one channel, usually with all the sound (in most
cases, music) coming from just one speaker system.-
- Moving-coil cartridge
A phonograph cartridge that makes use of a moving coil attached to the internal end of the
stylus assembly to excite a magnetic field in a frxed-magnet structure, producing an
electrical output for amplification. Rarely available these days, except as high-end audio
items, and electroacoustically no better than the moving-magnet design.-
- Moving-magnet cartridge
A phonograph cartridge that makes use of a moving magnet attached to its stylus assembly
to excite a magnetic field in a fixed-coil structure, producing an electrical output for
amplification.-
- Multipath distortion
In FM radio transmissions, this effect occurs when a signal, because of being reflected
from some surface (building, hill, etc.), arrives slightly later than the signals arriving
directly from the transmitter. Because of the nature of FM-stereo matrixing, it can cause
audible problems if the antenna and/or tuner is not well designed. In video, the effect
causes ghost images.
- NAB
The National Association of Broadcasters. -
- NR
Noise Reduction.-
- NTSC
The National Television System Committee. The body responsible for the color television
broadcast standards in the USA. The term NTSC is often applied to the performance
parameters of pre-HDTV video hardware and software in this country.-
- Near field
Technically, the region where the particle velocity is mostly out of phase with the sound
pressure-meaning that it can be very close to the listener at higher frequencies.
Popularly-and incorrectly-it is often considered to be any point where the direct sound is
significantly louder than the reflected sound.-
- Negative feedback
In all amplifiers, a part of the output signal that is fed back and added to the input
signal out of phase, somewhat reducing the gain, limiting distortion, and imparting
stability. Negative feedback, when used properly, can also improve frequency response. At
higher frequencies, the feedback may not be fast enough, and the result will be increased
transient intermodulation distortion. Under most conditions, this will not be audible.
Feedback may be used "locally," in sections of an amplifier, or
"generally," to control the response of the whole unit. See also TIM.-
- Noise floor
The noise generated by an audio device in the absence of any input signal.-
- Noise reduction: audio
A blanket term to describe a variety of background-noise-suppressing systems (Dolby, dbx,
CX, etc.), which are employed in audio and video sound systems. Even hi-fi video recorders
have proprietary audio noise-reduction circuitry. Most digital-audio systems do not
require it.-
- Noise reduction: video
On some VCRs and laser-video players, digital noise reduction is used to improve picture
quality, especially as it relates to video grain and snow in dark areas.-
- Noise shaping
Digital recording techniques that take advantage of the ear's reduced sensitivity at high
frequencies-
- Notch filter
In video systems, this removes a small part of the TV signal where color information is
most concentrated, reducing unwanted artifacts from less-than-perfect signals. See also
Comb filter
- Objective testing
The proper use of instrumentation or rigorously managed listening comparisons, rather than
casual or uncontrolled techniques, to evaluate audio or video equipment. See also Subjective testing.-
- Octave
A pitch interval or frequency ratio of two to one. Thus, a jump from 50 Hz to 100
Hz is one octave, as is a jump from 5,000 Hz to 10,000 Hz (5 kHz to 10 kHz). In listening
to musical programs, the interaction of ear and brain makes it difficult to resolve minor
frequency-response anomalies narrower than about a third of an octave.-
- Off-axis
Any listening, viewing, measuring, or recording position that is not directly in
front of the forward axis of a TV set, loudspeaker, or microphone.-
- Ohm
A basic unit of electrical resistance. See also Resistance; Impedance; Reactance.-
- Omni-directional microphone
A microphone that picks up wide-bandwidth sound equally well from all directions. A
variant is the subcardioid, which has somewhat less sensitivity in one direction-
- On-axis
Any listening, viewing, measuring, or recording position that is directly in front of a TV
set, loudspeaker, or microphone.-
- Open-reel recorder
A tape recorder that holds its tape in individual reels rather than cassettes. Reels vary
in diameter from 5 to 10 inches-
- Output impedance
The impedance seen by an electrical load attached to the output terminals of an audio or
video device. For practical purposes, the output impedance of any audio amplifying
equipment should be low in comparison to what it is connected to. It should not only be
low at low frequencies, where it will affect bass damping, but should also be low at
higher frequencies to insure a flat frequency response. In video systems, output and input
impedances should closely match.-
- Oversampling
In most digital playback equipment, the sampling frequency is increased two, four, or, in
the case of bitstream devices, even hundreds of times. However, the new samples are
artificially included between the originals and will not actually affect the 16-bit
information. What this digital filtering technique does is reduce the need for steep
analog filters to remove ultrasonic hash, saving the manufacturer and hopefully the
purchaser money. Although nearly all modern CD players use this technique in one form or
another, there is no evidence that oversampling markedly improves playback sound.
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