Dictionary of Audio Terminology - L
L - The electronic symbol for an inductor.
la - The sixth tone of the diatonic scale in solfeggio. [AHD]
LAB (Live Audio Board) - Topics related to sound reinforcement and application of audio for live events -- the most active pro audio forum on the Web, created by road dog Dave Stevens and hosted by ProSoundWeb.com.
lacquer crackers - Records, platters, waxings, discs. [Decharne]
LAeq - For airborne sounds that are non-stationary with respect to time, an equivalent continuous sound pressure level (see below) formed by applying A-weighting to the original signal before squaring and averaging. [Morfey] Abbreviated LAeq (15) for a time duration of 15 minutes.
Laff Box Invented by American sound engineer Charles Douglass (1910-2003) in 1953, it provided canned laughter for TV programs, including I Love Lucy.
lag – (1) The difference in phase between a current and the voltage that produced it, expressed in electrical degrees. (2) The delay in action of a sensing element of a control element. [ IEEE Std 241]
Lamarr, Hedy - (b. 1924-2000) Born Hedy Kiesler in Vienna, this Hollywood actress used her knowledge of musical harmony, along with composer George Antheil, to obtain a patent on technology for military communications in 1942, establishing the groundwork for today's spread-spectrum communication technology.
LAN (local area network) - A combination of at least two computers and peripherals on a common wiring scheme, which allows two-way communication of data between any devices on the network.
Lansing Iconic - The first recording studio monitor loudspeaker designed and manufactured by Lansing Manufacturing Company in 1927.
Laplace, Marquis Pierre Simon de - (b. 1749-1827) French mathematician and astronomer who formulated the theory of probability.
Laplace transform - A powerful circuit analysis technique that transforms difficult differential equations into simple algebra problems. Omitting all the mathematical details to get to the essence, the Laplace transform substitutes the Laplace operator "s" to represent complex frequency impedances. Therefore inductive reactance, XL is represented by "sL" and capacitive reactance, XC becomes 1/sC.
LARES (Lexicon Acoustic Reinforcement and Enhancement System) - The time-varying reverberation system invented and developed by David Griesinger while at Lexicon beginning in 1991.
Larsen Effect - The phenomenon where the sound from a loudspeaker is picked up by the microphone feeding it, and re-amplified out the same loudspeaker only to return to the same microphone to be re-amplified again, forming an acoustic loop. Each time the signal becomes larger until the system runs away and rings or feeds back on itself producing the all-too-common scream or squeal found in sound systems. These buildups occur at particular frequencies called feedback frequencies.
Larsen, Søren - (b. 1871-1957) Danish physicist (or physician -- both are seen; neither can be confirmed) notable for his contributions on acoustic feedback.
larynx - "The part of the respiratory tract between the pharynx and the trachea, having walls of cartilage and muscle and containing the vocal cords enveloped in folds of mucous membrane." [AHD].
laser (light amplification by stimulated emission of radiation) - A device that generates coherent, monochromatic light waves. All CD players contain a semiconductor laser in their optical pickup.
laser microphone - An entirely new type of microphone invented by David Schwartz that promises conversion of acoustical to electrical energy with zero distortion.
laser turntable - A phonograph that plays vinyl records using a laser instead of a cartridge so there is no contact between the record and the laser sensor.
last-on - Term referring to microphone inputs on an automatic mic mixer that stay on (open) until another mic input turns on. Contrast with gated-on. A last-on mic becomes a master mic if left open long enough.
LAT (linear array transducer) - Trademarked name for a new loudspeaker technology developed by Tymphany Corporation. For details see AES preprints #6191, 6247 and 6250.
latency - Used to describe the inherent delay in signal processing as well as software processing. The time it takes for a system or device to respond to an instruction, or the time it takes for a signal to pass through a device. It is how long it takes for a result to happen from a command. In telecommunications it is the length of time it takes packets to traverse the media.
laugh box - Invented by American sound engineer Charles Douglass (b. 1910-2003) in 1953, it provided canned laughter for TV programs, including I Love Lucy.
Lavaliere or lavaliere microphone - A small electret microphone designed to be worn on a person.
lay - In reference to Wire & Cable, to place together (strands) to be twisted into rope. To make in this manner: lay up cable. [AHD] The number of twists per unit length in twisted cable, called the lay. The helical arrangement formed by twisting together the individual elements of a cable. [IEEE]
layback - A post operation that rejoins audio and video after all other editing is complete.
LCD (liquid crystal display) - A display of numerical or graphical information made of material whose reflectance or transmittance changes when an electric field is applied. An LCD requires ambient light or backlighting for viewing.
LCR (left center right) - A three-channel sound system utilizing a left channel, a right channel and a center channel to stabilize the phantom images.
LDI (Live Design International) - The largest US trade show and conference focused on technologies for the live entertainment industry.
LDR (light-detecting resistor or light-dependent resistor) - An optoelectronic device whose resistance varies (inversely proportional) as a function of light ; a photocell, often constructed from CdS.
Leach Jr., William Marshall - (b. 1940-2010) American engineer and professor who made significant contributions to audio engineering throughout his life, including authoring 26 JAES papers.
lead-acid battery - A storage battery in which the active material of the positive plate is lead dioxide, the negative plate is lead, and the electrolyte is dilute sulfuric acid. [ IEEE Std 1578]
Lear cartridge (aka 8-track cartridge) - Invented by William Powell Lear, the man behind the LearJet; eventually superceded by the compact cassette.
LeBel, C. J. - (b. 1901-1960) American inventor and founder and first president of the Audio Engineering Society.
Leccese, Albert - (b. 1953-2010) American engineer who helped pioneer touring sound as Director of Engineering at Audio Analysts.
LED (light-emitting diode) - Invented by Nick Holonyak, Jr. in 1962, a self-lighting semiconductor display of numerical or graphical information based on the light emitting characteristics of a solid-state device that emits incoherent (i.e., random direction) light when conducting a forward current.
LEED® (Leadership in Energy and Environmental Design) - A registered trademark of USGBC (US Green Building Council) An environmental rating system for the building industry -- a "benchmark for the design, construction, and operation of high performance green buildings."
egacy devices - Something handed down from an ancestor, or a predecessor, or something from the past [AHD]. Used in the computer world to refer to yesterday's solutions, for example including an RS-232 port on a USB machine.
LEO (low earth orbit) - Term referring to communications satellites positioned 200-900 miles (320-1450 kilometers) high.
lepatata - A trumpet-shaped horn indigenous to South Africa
Leq - Symbol for equivalent continuous sound pressure level.
Leq(A) - Symbol for equivalent continuous sound pressure level (A-weighted). Also seen as LAeq.
Leslie™ - A special loudspeaker design made famous by its use with the Hammond B-3 organ, featured prominently in much of the 1960's and 1970's music (Procol Harum, et al.) characterized by a swirling pitch-shifting sound.
Les Paul - (b. 1915-2009) [Birth name: Lester William Polsfuss] American musician legend who was also a gifted songwriter and inventor. His pioneering work on the solid-body electric guitar and multitrack recordings changed the pro audio industry forever.
LEV - Acronym for listener envelopment. [Morfey]
leveler - A dynamic processor that maintains (or "levels") the amount of one audio signal based upon the level of a second audio signal. Normally, the second signal is from an ambient noise sensing microphone.
levels - Terms used to describe relative audio signal levels.
line-level - Standard +4 dBu or -10 dBV audio levels.
instrument-level Nominal signal from musical instruments using electrical pick-ups. Varies widely, from very low mic-levels to quite large line-levels.
Leyland number - Any number that can be expressed as xy+ yx, e.g., 593 = 29 + 92. Hit the link to see other examples.
LFE (low frequency effects) - Popularly called bass management, but this is technically wrong. The "point-one" in "5.1 surround systems". It refers to the limited bandwidth (20-90 Hz, 20-120 Hz, or 20-150 Hz depending on the encoding system) special effects/feature channel, but can also refer to a subwoofer channel.
LFO (low frequency oscillator) - A very low frequency (less than 10 Hz) sine wave oscillator used to slowly vary other parameters to create effects like flanging and tremolo, or vibrato.
licorice stick - Clarinet. [Decharne]
LIDAR (light detection and ranging) - A system based on the same principles as RADAR developed for locating, ranging and profiling applications.
lift/dip - Popular European term meaning boost/cut.
light organ - Electronic device popular in the '60s and '70s where different colored lights would flash in response to different musical frequencies. Contrast with color organ.
light pipe or light guide - A device made from optical plastic that couples light from a source (usually a surface mounted LED) to a user interface panel. Design and theory here.
light wave coupling (LWC) - Experimental very flexible flat panel display technology under development at Extreme Photonix, a University of Cincinnati spin-off from their Nanoelectronics Laboratory.
Lilith or Lilith Fair - An all-women festival tour begun in 1997 by artist Sarah McLachlan along with Dan Fraser, Marty Diamond and Terry McBride, as a celebration of women in music.
limelight - (A) An early type of stage light in which lime was heated to incandescence producing brilliant illumination. (b) The brilliant white light so produced. Also called calcium light. [AHD]
Limestone - The Greek theater of Epidaurus is considered one of the most extraordinary acoustic spaces of antiquity. A study by Nico F. Declercq and Cindy Dekeyser of the Georgia Institute of Technology concluded that it was the use of limestone in the seats that created its wonderful acoustic qualities.
limiter - A compressor with a fixed ratio of 10:1 or greater. The dynamic action effectively prevents the audio signal from becoming any larger than the threshold setting. For example, if the threshold is set for, say, +16 dBu and the input signal increases by 10 dB to +26 dB, the output only increases by 1 dB to +17 dBu, essentially remaining constant.
Line arrays (also called articulated line arrays) - A vertical line (or linear) configuration for large venue multi-cabinet loudspeaker systems creating tight (and steerable) beamwidth coverage (degrees of arc for the propagating sound wave, vertically and horizontally).
line driver - A balanced output stage designed to interface and drive long lines. Long output lines tax output stages in terms of stability and current demands. Designs vary from direct-drive differential (sometimes using cross-coupled techniques) to transformer drive.
line echo canceller - used to suppress electrical echoes caused by the transmission link itself.
linear array transducer - Trademarked name for a new loudspeaker technology developed by Tymphany Corporation. For details see AES preprints #6191, 6247 and 6250.
linear distortion - Any change to the amplitude or phase of the incoming signal frequency components. Contrast with nonlinear distortion.
linear PCM - A pulse code modulation system in which the signal is converted directly to a PCM word without companding, or other processing.
linear phase response - Any system which accurately preserves phase relationships between frequencies, i.e., that exhibits pure delay.
linear system or linear device - A system or device that meets two criteria: (1) proportionality -- the output smoothly follows the input; (2) additivity -- if input x results in output U and input y results in output V, then input x+y must result in output U+V. This means the system or device is predictably and its cause and effect relationship is proportional. Contrast: nonlinear.
linear taper (aka B-taper) - Always 50% resistance at the 50% travel point.
linear time code (LTC) - an encoding of SMPTE timecode data in an audio signal, as defined in SMPTE 12M specification.
linearity error - The maximum permissible deviation of the actual output quantity from a reference curve or line.
line-level - Standard +4 dBu or -10 dBV audio levels.
Linkwitz-Riley crossover - The de facto standard for professional audio active crossovers is the 4th-order (24 dB/octave slopes) Linkwitz-Riley (LR-4) design. Consisting of cascaded 2nd-order Butterworth low-pass filters, the LR-4 represents a vast improvement over the previous 3rd-order (18 dB/octave) Butterworth standard.
Linux - A computer Unix-type operating system (OS) invented by Linus Torvalds in 1992, who wrote it as a student at the University of Helsinki. He created this OS because he couldn't afford one that could accomplish what he wanted with his available hardware. He then posted it on the network for other students, where it grew and became very stable and powerful. Today, for free, the software, source code, etc., is available off the Web.
LIPA (Liverpool Institute for Performing Arts) - A state-of-the-art performing arts higher education institution co-founded by Paul McCartney and Mark Featherstone-Witty; located in a renovated old school that McCartney went to.
Lissajous figure also Lissajous curve and Bowditch curve - (after Nathaniel Bowditch, in 1815 who first studied these curves). A special case of X-Y plot in which the signals applied to both axes are sinusoidal functions. For a stable display the signals must be harmonics. Lissajous figures are useful for determining phase and harmonic relationships. (After J. A. Lissajous) [IEEE]
Lissajous, Jules Antoine - (b. 1822-1880) French mathematician.
liter Abbr. l or lit. - A metric unit of volume equal to approximately 1.056 liquid quarts, 0.908 dry quart, or 0.264 gallon. [AHD]
litz wire - Derived and shortened from the German word "litzendraht" meaning strand, or woven wire. It is a cable constructed of individually insulated magnet wires either twisted or braided into a uniform pattern, which increases the total surface area compared to an equivalent solid conductor. The pattern is formed to reduce skin effect by guaranteeing that along a significant length, any single conductor will be, for some portion of its length, located in the center, the middle, and the outer portion of the bundle. This transposition prevents any one conductor from being subject to the full forces of magnetic flux, thereby reducing the effective resistance of the entire bundle. Litz wire bundles of 50, 100 or even more conductors are available. They are constructed by winding smaller bundles of six conductors into larger bundles. Those bundles may be "litzed" with other bundles to create progressively larger cables. Litz constructions counteract skin effect by increasing the amount of surface area without significantly increasing the size of the conductor.
liuqin - Chinese 4-string mandolin.
LKFS (loudness K-weighted digital full scale) - A standard ( ITU R BS.1770-2) aimed at normalizing broadcast loudness levels. An increase of 1 dB in signal level will cause the loudness reading to increase by 1 LKFS.
lobing error - The amount of on-axis deviation in amplitude from zero (i.e., perfect combined radiation pattern) resulting from phase deviations at the crossover point. Term coined by Lipshitz (Lipshitz, Stanley P. and John Vanderkooy, "A Family of Linear-Phase Crossover Networks of High Slope Derived by Time Delay," J. Audio Eng. Soc., Vol. 31, No. 1/2, January/February 1983, pp. 2-20).
lodestone (also loadstone) - A piece of magnetite that has magnetic properties and attracts iron or steel. [AHD]
log - Short for logarithm.
Logarithm - A shortcut method that uses the powers of 10 (or some other base) to represent the actual number. The logarithm is the power to which a base, such as 10, must be raised to produce a given number. For example, 10³ = 1,000; therefore, log (to the base 10) 1,000 = 3. The types most often used are the common logarithm (base 10), the natural logarithm (base e), and the binary logarithm (base 2).
logic - A system of reasoning first formulated by Aristotle. (1) The study of the principles of reasoning, especially of the structure of propositions as distinguished from their content and of method and validity in deductive reasoning. In reference to Computer Science (a) The nonarithmetic operations performed by a computer, such as sorting, comparing, and matching, that involve yes-no decisions. (b) Computer circuitry. (c) Graphic representation of computer circuitry. [AHD]
log taper (aka D-taper) - Often used as an audio taper since its 50% rotation point has 10% resistance.
Long, Richard - (b. 1933-1986) Founder of RLA (Richard Long and Associates), dance club sound designers during the disco heydays of the '70s and '80s.
Longitudinal - Of or relating to longitude or length. [AHD]
long-tailed pair - The most common form of differential amplifier usually consisting of a top-side current mirror and a constant bias current source tied to the common emitters point, forming the "tail." First designed and patented by Alan Blumlein in 1936 as an amplifier for small signals.
loop - A closed circuit, i.e., a set of branches forming a closed current path, provided that the omission of any branch eliminates the closed path. An electric circuit providing an uninterrupted path for the flow of current.
loopback address - Pinging yourself by using IP address 127.0.0.1
Lorentz force - The orthogonal (right angle) force on a charged particle traveling in a magnetic field, named after H. A. Lorentz. [AHD]
Lorentz, Hendrik Antoon - (b. 1853-1928) Dutch physicist, famous for the Lorentz force and co-receiving a Nobel Prize for researching the influence of magnetism on radiation. [AHD]
Lossless – In reference to audio compression, data that is not lost due to the compression scheme.
Lossy - In reference to audio compression, data which is lost due to the compression scheme
loudness - The SPL of a standard sound which appears to be as loud as the unknown. Loudness level is measured in phons and equals the equivalent SPL in dB of the standard.
loudness curve or Fletcher-Munson curves - In the '30s, researchers Fletcher and Munson first accurately measured and published a set of curves showing the human's ear's sensitivity to pure tone loudness verses frequency ("Loudness, its Definition Measurement and Calculation," J. Acoust. Soc. Am., vol. 5, p 82, Oct. 1933).
loudspeaker - An electromagnetic transducer based on the principle of electromagnetic induction used to convert the electrical energy output of a power amplifier into acoustic energy. The heart of a dynamic loudspeaker is a coil of wire (the voice coil), a magnet, and a cone.
loudspeaker directivity - Used to connote the directivity, or a measure of the directional characteristic of a loudspeaker, and is called the Directivity Index, either measured in decibels, or as a dimensionless value of Q
loudspeaker line arrays (also called articulated line arrays) - A vertical line (or linear) configuration for large venue multi-cabinet loudspeaker systems creating tight (and steerable) beamwidth coverage (degrees of arc for the propagating sound wave, vertically and horizontally).
loudspeaker model or amplifier dummy load - Modeling a real world loudspeaker for power amplifier testing purposes has been studied for years, resulting in many circuit possibilities.
loudspeaker reconing - The act of replacing a blown, torn, or cracked cone on a dynamic loudspeaker -- a highly skilled operation.
loudspeaker sensitivity - The standard is to apply one watt and measure the sound pressure level (SPL) at a distance of one meter. [IEC 60268-5]
loudspeaker surround - The circular ring mechanism that attaches the cone to the frame ("surrounding" the cone), usually rolled (allows greater throw) and made from foam or rubber material.
low-cut filter also lo-cut filter See high-pass filter [In audio electronics, we define things like this just to make sure you're paying attention.] Contrast with low-pass filter below.
low impedance Abbr. Lo-Z - A device having an electrical impedance of at less than 1,000 ohms. [Note: This value is arbitrary as there is no standard defining exactly what constitutes a 'low impedance.'] Examples include loudspeakers in the 4-16 ohms range; headphones from 32-150 ohms; microphones rated 50-600 ohms; and electronic circuit outputs are low-impedance, rated at 50-300 ohms. Contrast with high impedance.
low-pass filter also lo-pass filter - A filter having a passband extending from DC (zero Hz) to some finite cutoff frequency (not infinite). A filter with a characteristic that allows all frequencies below a specified rolloff frequency to pass and attenuate all frequencies above. Anti-aliasing and anti-imaging filters are low-pass filters. Also known as a high-cut filter.
low voltage - A term with many definitions, some of which surprise, like that 1000 Vac is considered "low voltage" by the IEC.
L-pad - A two-leg network shaped like an inverted, backward letter "L". It usually consists of two resistors that are fixed or adjustable.
LRAD (long range acoustic device) - A non-lethal sonic communicator/weapon developed by American Technology Corporation capable of producing sound pressure levels of 153 dB-SPL.
LRC (inductance-resistance-capacitance) - Shorthand for the most common passive circuit elements. Also seen as RLC, LCR, CRL, etc.
LSB (least significant bit) - The bit within a digital word that represents the smallest possible coded value; hence, the LSB is a measure of precision.
LTC (linear time code) - an encoding of SMPTE timecode data in an audio signal, as defined in SMPTE 12M specification. The audio signal is commonly recorded on a VTR track or other storage media.
LUFS (loudness unit digital Full Scale) - Alternate term for LKFS.
Lully, Jean-Baptiste - (b. 1632-1687) French composer. [AHD]
Lumière, Auguste and Louis - French brothers who invented the "cinematograph," reportedly the first all-in-one camera/projector/printer, in 1895.
luminance - (1) Abbreviated Y. That part of the video signal that carries the information on how bright the TV signal is to be. The black and white signal.
Lunchbox - Nickname for the narrow 500 Series of modular card frame racks. Coined by Art Kelm. "API Lunchbox" is a registered trademark of API Audio.
lute - A stringed instrument having a body shaped like a pear sliced lengthwise and a neck with a fretted fingerboard that is usually bent just below the tuning pegs. [AHD]
LWC (light wave coupling) - Experimental very flexible flat panel display technology under development at Extreme Photonix, a University of Cincinnati spin-off from their Nanoelectronics Laboratory.
lyra - Three stringed bowed instrument with a bowl back carved from the solid. Popular in Greece and the Balkans.
lyre - A stringed instrument of the harp family having two curved arms connected at the upper end by a crossbar, used to accompany a singer or reciter of poetry, especially in ancient Greece. [AHD] One of the oldest known musical instruments dating back to the Sumerians.
lyric - French word literally meaning of a lyre; the words of a song.
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