L The electronic symbol for an inductor.
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]
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 Electronics. 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 (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.
LAMC (Latin Alternative Music Conference) A yearly conference held in NY City, usually in July, featuring latin alternative music.
Lansing Iconic Loudspeaker. The first recording studio monitor loudspeaker designed and manufactured by Lansing Manufacturing Company in 1927. Hit the link for pictures and details.
Laplace, Marquis Pierre Simon de (1749-1827) French mathematician and astronomer who formulated the theory of probability.
Laplace transform Electronic circuit analysis. 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. Details here: Improving Room Acoustics through time-variant synthetic reverberation by David Griesinger. This is an example of an EAE system.
Larsen, Søren (1871-1957) Danish physicist (or physician -- both are seen; neither can be confirmed) notable for his contributions on acoustic feedback. [Write me if you can direct me to a biography for Larsen. I cannot find one.]
larynx See voice box.
laser microphone Microphones. An entirely new type of microphone invented by David Schwartz that promises conversion of acoustical to electrical energy with zero distortion.
laser turntable Phonographs. 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. Beginning at $15,000, it is not cheap, but very innovative.
last-on Teleconferencing. 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.
latency Similar to propagation delay but broader in application. 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 See Laff Box.
lavaliere or lavaliere microphone A small electret microphone designed to be worn on a person. The first lavaliere mics were worn around the neck on a lanyard, hence the French name lavallière, a type of necktie, used to describe a pendant worn on a chain around the neck (after the Duchess de La Vallière who started the fashion [AHD]). Today most lavaliere (the final "e" is commonly dropped) mics are attached by clips rather than hung from a cord.
lawful "Compatible with the will of a judge having jurisdiction." -- Ambrose Bierce.
lawyer "One skilled in circumvention of the law." -- Ambrose Bierce.
lay 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 Recording. 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) Sound Reinforcement. 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.
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]
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. See LEVD.
LEDE (live end-dead end) Acoustics. Recording studio acoustic treatment developed by Chips Davis in the late '70s where a room is designed to have a live end, i.e., reverberant and a dead end (opposite) that is heavily damped. Hit the link for the original AES paper written by Chips Davis and Don Davis (no relation) in 1980.
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." See RaneNote: LEED and the MA 4 Multichannel Amplifier.
Leet Internet-based written slang, e.g., "leet" is Internet slang for "elite," "L8tr" for "later," and "l00kin6" for "looking, etc. Used to encrypt text messages, but it is much more sophisticated than the elementary "B4" for "before." It is a complicated use of letters and numbers that look like letters, e.g., "m4d" for "mad."
legacy 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) Telephony. Term referring to communications satellites positioned 200-900 miles (320-1450 kilometers) high.
lepatata See: vuvuzela
Leq Symbol for equivalent continuous sound pressure level.
Leslie™ Loudspeaker. 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. Designed in the 1940s by Don Leslie, it uses a fixed loudspeaker and a rotating horn assembly to cause a doppler sound effect.
Les Paul See: Paul, Les
LEV Acoustics. 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. For example, a restaurant is a typical application where it is desired to maintain paging and background music a specified loudness above the ambient noise. The leveler monitors the background noise, dynamically increasing and decreasing the main audio signal as necessary to maintain a constant loudness differential between the two. Also called ambient noise compensator and SPL (sound pressure level) controller.
levels Terms used to describe relative audio signal levels: (Also see decibel).
lexicographer The author of a lexicon or dictionary. "Every other author may aspire to praise; the lexicographer can only hope to escape reproach; and even this negative recompense has been yet granted to very few." -- Samuel Johnson, 1755.
Leyland number Mathematics. Any number that can be expressed as xy+ yx, e.g., 593 = 29 + 92. Hit the link to see other examples.
LFD (low-frequency diffusion) Acoustics.
LFE (low frequency effects) [Note: it is "effects" NOT "enhancement".) 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. Both Dolby Digital and DTS Consumer use the term. The "bass management" part comes from having the option of leaving the bass in the five full-range channels or sending all the lower bass to the subwoofer, or some combination.
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 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 See LWC.
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 Acoustics. See: Epidaurus.
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. Used primarily for preventing equipment, media, and transmitter overloads. A limiter is to a compressor what a noise gate is to an expander. See the RaneNote "Dynamics Processors -- Technology & Applications."
line arrays Loudspeakers. (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). Favored for their controlled directivity that reduces room reflections and produces less reverberation and improved sound intelligibility, as well as reducing the sound that bleeds back onto the performers. The three most popular configurations are (a) uniform array: typically 2-8 boxes arranged in a flat straight line popular in smaller venues and usually tilted downward above the audience; (b) constant splay array: forms a smooth arc by tilting each box the same amount (pitch) resulting in a wider beamwidth popular in concert hall settings, particularly those with balconies; (c) progressive splay array: combines both previous examples by starting out with a straight flat array that gradually creates an arc at the lower end, forming the letter "J" like shape. Popular for large arenas and concert settings. Individual and unique variations are offered by all major loudspeaker companies.
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. See the RaneNote Practical Line Driving Current Requirements.
line echo canceller See echo canceller.
linear array transducer See LAT.
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. See group 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 See potentiometer.
linear time code See time code.
linearity error Electronics. The maximum permissible deviation of the actual output quantity from a reference curve or line. Think of it as an error-window surrounding the reference: anywhere inside is okay, anywhere outside is not. The size of the window is the linearity error.
line-level See levels.
line source arrays See: line arrays.
linguistics The study of the nature, structure, and variation of language, including phonetics, phonology, morphology, syntax, semantics, sociolinguistics, and pragmatics. [AHD]
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. Named after S. Linkwitz, a Hewlett-Packard engineer at that time, who first described the problems and solution in his paper "Active Crossover Networks for Non-coincident Drivers," J. Audio Eng. Soc., vol. 24, Jan/Feb 1976, pp. 2-8. In this paper, he credited his co-worker Russ Riley for the idea that cascaded Butterworth filters met all his crossover requirements. Their effort became known as the Linkwitz-Riley alignment. Linkwitz showed that a significant weakness of the Butterworth design was the behavior of the combined acoustic lobe along the vertical axis. An acoustic lobe results when both drivers operate together reproducing the crossover frequency band, and in the Butterworth case it exhibits severe peaking and is not on-axis (it tilts toward the lagging driver). Linkwitz showed that this results from the Butterworth outputs not being in-phase. Riley demonstrated an elegant solution by cascading two 2nd-order (any even-ordered pair works) Butterworth filters, which produced outputs that were always in-phase and summed to a constant-voltage response. Thus was created a better crossover. See the RaneNote Linkwitz-Riley Crossovers: A Primer and RaneNote Signal Processing Fundamentals.
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. History here.
Lissajous figure also Lissajous curve and Bowditch curve (after Nathaniel Bowditch, in 1815 who first studied these curves) Oscilloscopes. 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] For some educational fun check out Lissajous Lab. Also fun is Crop Circles of Consciousness.
Lissajous, Jules Antoine (1822-1880) French mathematician.
listening "It is the province of knowledge to speak and it is the privilege of wisdom to listen." Oliver Wendel Holmes [Crystal]
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.
live sound See: History of Concert Sound.
LKFS (loudness K-weighted digital full scale) Broadcast. 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. For a particularly good overview see: Florian Camerer's paper, "On the way to Loudness nirvana: audio levelling with EBU R128." Also see: LUFS.
load shedding Power Supplies. Term for any sort of automatic rationing of available power when demand exceeds capacity. When power companies do this it is commonly called a rolling blackout.
lobing error Electronic crossovers. 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, 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). See the RaneNote Linkwitz-Riley Crossovers: A Primer.
Loft Scene Musical jazz and early hip-hop phenomenon occurring in New York city during the '70s, where people would dance and party in renovated old industrial loft spaces.
log Short for logarithm.
logarithm Mathematics. 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. Computer Science
log taper See potentiometer.
Long, Richard (1933-1986) Founder of RLA (Richard Long and Associates), dance club sound designers during the disco heydays of the '70s and '80s. Richard's success grew out of his experience working as the sound engineer for the Paradise Garage in Greenwich Village during the mid-seventies. After developing his chops at the Paradise Garage, Richard designed many famous dance clubs including Studio 54, Annabel's (London), Regine's (a chain of 19 clubs scattered around the world from Paris and NY to Cairo) and many others that were the vanguard of the disco era. Indeed, continuing years beyond Richard's unfortunate death in 1986, his designs flourish today in such icons as the Ministry of Sound (London). Further information available at GSA and see Richard and Alan Fierstein's seminal paper "State-of-the-Art Discotheque Sound Systems -- System Design and Acoustical Measurement," presented at the 67th Convention of the Audio Engineering Society, New York , 1980, preprint 1694.
Longacre Square Original name for Times Square; renamed in 1904.
longitudinal Of or relating to longitude or length. [AHD]
long-tailed pair Analog Electronics. 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 (wasn't everything!) in 1936 as an amplifier for small signals.
loop Electronic circuits. 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 Internet. Pinging yourself by using IP address 127.0.0.1
loss See gain.
lossless See digital audio data compression
lossy See digital audio data compression.
loud Having offensively bright colors: a loud necktie. [AHD]
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. [For example, a sound judged as loud as a 40 dB-SPL 1 kHz tone has a loudness level of 40 phons. Also, it takes 10 phons (an increase of 10 dB-SPL) to be judged twice as loud.] Note that loudness is a subjective measurement; contrast with intensity which is an objective measurement.
loudness curve See Fletcher-Munson.
loudspeaker, acoustic suspension See: acoustic suspension loudspeaker.
loudspeaker Dynamic. 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. The amplifier applies
voltage to the voice coil causing a current to flow that produces a magnetic
field that reacts with the stationary magnet making the cone move proportional
to the applied audio signal.
loudspeaker directivity See: Q.
loudspeaker line arrays See line arrays.
loudspeaker model See amplifier dummy load.
loudspeaker reconing See reconing.
loudspeaker sensitivity See sensitivity.
loudspeaker surround See surround.
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 Electronics. 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 Electricity. A term with many definitions, some of which surprise, like that 1000 Vac is considered "low voltage" by the IEC.
Lo-Z See low impedance.
L-pad See attenuator pad.
LTC (linear time code) See time code.
LUFS (loudness unit digital Full Scale) Alternate term for LKFS.
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. 2. VJ Jargon. A filter that controls the video brightness. Used to blend clips by limiting the bright or dark image pixels. See chrominance.
LWC (light wave coupling) Electronic Displays. Experimental very flexible flat panel display technology under development at Extreme Photonix, a University of Cincinnati spin-off from their Nanoelectronics Laboratory.
Lynard Skynyrd American rock band who took their name from their high school gym teacher, Leonard Skinner, as a way of mocking him, since he was a strict disciplinarian and had their guitarist, Gary Rossington, kicked out of school for having hair too long.
lyra Musical Instruments. Three stringed bowed instrument with a bowl back carved from the solid. Popular in Greece and the Balkans.
lyre Musical Instruments. 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.