"U" Abbreviation for the "modular unit" on which rack panel heights are based. Per the EIA and ANSI standard ANSI/EIA-310-D-1992 Cabinets, Racks, Panels, and Associated Equipment, the modular unit is equal to 44.45 millimeters (1.75"). Panel heights are referred to as "nU" where n is equal to the number of modular units. Examples are 1U (1.75" high), 2U (3.5" high), 3U (5.25" high), etc. Popularly called rack units and often abbreviated "RU," which is technically incorrect but not misleading.

UART (universal asynchronous receiver-transmitter) The device that performs the bidirectional parallel-to-serial data conversions necessary for the serial transmission of data into and out of a computer.

uber or über A German term that literally means 'over,' but which is used in academia to refer to the fundamental essence of a concept or idea. Popularly used to mean 'very' or 'really,' as in "Rane audio is uber audio." Hit the link to read 100 different definitions.

ud Musical Instrument. See: oud.

UDP (user datagram protocol) A TCP/IP protocol describing how messages reach application programs within a destination computer. This protocol is normally bundled with IP-layer software (UDP/IP). UDP is a transport layer, connectionless mode protocol, providing a datagram mode of communication for delivery of packets to a remote or local user. UDP/IP has almost no error recovery services, and is used primarily for broadcasting messages over a network.

UDP/IP (user datagram protocol/internet protocol) See: UDP above.

udu drum Musical Instrument. A clay pot with two holes, cupped alternatively; sound produced by compression and release of the air inside it. [Glossary of Folk Musical Instruments & Styles from Around the World.]

ugh Used to express horror, disgust, or repugnance. [AHD] An example of an onomatopoeia word.

UHF See frequency bands.

UHJ (Universal HJ) A method of encoding three or four audio channels down to two channels, developed for use in Ambisonics playback on mono or stereo systems. "H" and "J" are simply code letters adopted by the BBGC, and have no other meaning. [ White]

UI (user interface) As compared with GUI.

uilleann pipes (pronounced: illan) Musical Instrument. A Celtic bagpipe whose air supply is produced by a bellows held under the arm and operated by the elbow. Often used in the plural. [AHD] Also called union pipes.

ukelin Musical Instrument. A bowed stringed instrument that combines the Hawaiian ukulele (uke) with the violin (lin). [From link.]

ukulele also ukelele Musical Instrument. A small four-stringed guitar popularized in Hawaii. [AHD]

UL (Underwriters Laboratories, Inc.) A private, for profit, testing laboratory approved by OSHA as a National Recognized Testing Laboratory (NRTL).

ULD (ultra low delay coder) One of Fraunhofer's (creator of MP3) proprietary forms of digital audio compression.

ULF (ultralow frequency) An electromagnetic wave whose frequency is less than 3,000 hertz. [AHD]

ULSI (ultra-large-scale integration) A logic device containing a million or more gates.

ultra-directional sound systems Loudspeakers. Pioneered by Dr. F. Joseph Pompei in the late '90s while a grad student at MIT, and patented as US Patent 6,775,388, Ultrasonic Transducers, granted 2004, this technology allows audio reproduction with extreme directionality. Using this technology sound can be literally spotlighted to whatever location is desired, producing audio at that spot only with very minimal leakage. While the ultrasonic transmission is not audible, it works by creating intermodulation frequency products at the beam's end that are audible.

ultraharmonic response Frequencies that are not whole number multipliers but fractional multiples of the fundamental frequency of the system, e.g. 1.5 or 2.5 times the fundamental frequency. Contrast with harmonic.

Ultra Music Festival See: UMF.

ultrasonic Of or relating to acoustic frequencies above the range audible to the human ear, or above approximately 20,000 hertz. [AHD] Compare with supersonic.

ultrasonography 1. Diagnostic imaging in which ultrasound is used to image an internal body structure or a developing fetus. Also called echography. 2. An imaging technique that uses high frequency sound waves to visualize underwater surfaces, boundaries, objects, and currents. [AHD]

ultrasound Acoustics. Sound at ultrasonic frequencies in any medium. Medicine. The use of ultrasonic waves for diagnostic or therapeutic purposes, specifically to image an internal body structure, monitor a developing fetus, or generate localized deep heat to the tissues. [AHD]

ululate To howl, wail, or lament loudly. [AHD]

U-matic Recording. Sony's trademarked name for their 3/4" helical-scan professional videocassette technology.

umbra 1. A dark area, especially the blackest part of a shadow from which all light is cut off. 2. Astronomy
a. The completely dark portion of the shadow cast by the earth, moon, or other body during an eclipse. b. The darkest region of a sunspot. [AHD]

UMF (Ultra Music Festival) Yearly huge dance festival held originally in Miami, now expanded to multiple cities.

umlaut 1. a. A change in a vowel sound caused by partial assimilation especially to a vowel or semivowel occurring in the following syllable. b. A vowel sound changed in this manner. Also called vowel mutation. 2. The diacritic mark (¨¨) placed over a vowel to indicate an umlaut, especially in German. [AHD]

umpo "In music, taking a song or a part of a song up tempo, or faster." Pseudodictionary.com Compare with: dempo.

UMRK (Utility Muffin Research Kitchen) Name of Frank Zappa's original recording studio completed in 1979.

una corda Music. With the soft pedal (the leftmost of a piano's three pedals) of the piano depressed. Used chiefly as a direction. [Italian: una, one + corda, string (so called because depressing the soft pedal causes only one string to be struck of the two or three provided for each note).] [AHD]

unbalanced line See balanced line.

unbalanced output Electronics. An amplifier, or other line-driving device, with one leg at ground potential.

unblooped Film Sound. Pertaining to motion-picture soundtrack negative wherein the discontinuities due to splices have not been minimized by making opaque the area near the splice with "bloopiing" tape or ink. [Holman]

uncertainty principle See Heisenberg uncertainty principle.

undamped Physics. Not tending toward a state of rest; not damped. Used of oscillations.

undamped frequency Electronics. Of a second-order linear system without damping, the frequency of free oscillation in radians per unit time or in hertz. [IEEE]

underdamped Electronics. Damped insufficiently to prevent oscillation of the output following an abrupt input stimulus. [IEEE]

underground (music) Any avant-garde, experimental, or subversive movement in popular art, films, music, etc. [Collins]

undersampling The use of too low a sampling frequency, resulting in aliasing.

underwater acoustics The science of sound propagation in the sea, and of sound radiation and scattering by underwater objects. [Morfey]

underwater sound projector A transducer used to produce sound in water. [IEEE]

unenclosed Pipe Organ Musical Instrument. "Unenclosed pipes are located in a visible position and are therefore able to project their tones directly into the room (vs. enclosed in a Swell box). Frequently, organs will have both the Great and pedal divisions unenclosed giving them a greater presence and clarity." [D.L. Simmons & Company Church Organs]

unicasting Networks. One-to-one communication (as opposed to broadcasting or multicasting).

unicasting Bundle CobraNet. One-to-one routing of audio on the network.

Unicode A universal system that provides a unique number for every character, regardless of platform, program, or language.

unidirectional microphone or just directional microphone One that is most sensitive to sound arriving directly at its front. Compare with omnidirectional mic and cardioid microphone.

Unidyne™ Microphones. Shure Model 55 Unidyne microphone designed by Benjamin Bauer and first sold in 1939
was the first single-element unidirectional microphone. Its performance qualities and distinctive styling ultimately make it “the most recognized microphone in the world.” [Shure History]

unification Pipe Organ Musical Instruments. "The process by which a set of pipes is extended and switched to allow for playing at various pitch levels (16', 8', 4', 2', 2-2/3', etc.) thereby increasing the instruments versatility." [D.L. Simmons & Company Church Organs]

uniform array See line arrays.

uniform coverage horn See constant directivity (CD) horn.

unilay Wire and Cable. A conductor with more than one layer of helically laid wires with the direction of lay and length of lay the same for all layers. [Belden}]

unimorph Piezoelectric Microphones. A cantilever device having one active piezoelectric layer and one inactive non-piezoelectric layer. Compare with: bimorph.

union pipes See: uilleann pipes

un poco Music. Meaning "a little," "small."

unisono Music. To perform in unison or octaves —used as a direction in ensemble music. [MWD]

units of measurement See Rowlett's How Many? A Dictionary of Units of Measurement for a valuable list (with definitions) of the International System of Weights and Measures, the metric system, and all English customary units. Very highly recommended.

unity gain A gain setting of one, or a device having a gain of one, i.e., it does not amplify or attenuate the audio signal. The output equals the input. See the RaneNote Unity Gain and Impedance Matching: Strange Bedfellows.

unity gain bandwidth See GBW.

unity power factor In an AC circuit, a power factor equal to one, which only occurs when the voltage and current are in phase, i.e., for a purely resistive circuit, or a reactive circuit at resonance.

unmodulated track Film Sound. An optical soundtrack containing no deliberate signal. For variable-area soundtracks, unmodulated track is made narrow when there is no signal present to reduce the noise caused by the optical grain of the film. [Holman]

unobtainium Reference to all those parts necessary to keep legacy audio devices running that you can never find — things like old ICs, connectors, etc. [Origin unknown, but thanks to CD for passing it on.]

upbeat Music. 1. An unaccented beat or beats that occur before the first beat of a measure. Also called anacrusis and pickup.
2. The upward stroke made by a conductor to indicate the beat that leads into a new measure. [AHD]

upcut Broadcast. Chopping off the beginning of the audio or video of a shot or video story.

upfader The name for the slide controls found on DJ mixers, typically two to four, used to increase (bring up) the level of the source controlled by each channel.

Upping some real crazy riffs. Playing cool music. [Decharne]

uproar Disorderly tumult together with loud, bewildering sound; a heated controversy. [AHD]

UPS (uninterruptible power supply) A back-up battery-powered supply (commonly used with computers) that automatically continues to supply power when the main AC source fails. Variations exist where the system always runs from the UPS (the AC line keeps the batteries charged when present), offering immunity from AC line fluctuations and noise.

upstage Theater. The back of the stage farthest from the audience, as opposed to downstage.

uptempo Music. A fast or lively tempo, as in jazz. [AHD]

upward expander See expander.

Urban Dictionary A slang dictionary of user made up definitions, as if the English language isn't difficult enough already. You makes 'um up as yus needs 'em folks.

URL (uniform resource locator) A Web address. A consistent method for specifying Internet resources in a way that all Web browsers understand. For example, "http://www.rane.com," is the URL for Rane's home page on the web. The "http" part tells the Web browser what protocol to use, and the remainder of the URL, "www.rane.com," is the Internet address.

ursatz (Ger.: 'fundamental structure') Music. Term used in Schenkerian analysis for the basic contrapuntal design that underlies the structure of a piece, reached by a process of reduction of the work's structural levels or layers and representing its ultimate 'background'. [Sadie]

urtext (Ger.: 'original text') Music. Term applied to a modern printed edition of earlier music in which the aim is to present an exact text without editorial additions or alterations. [Sadie]

USB (universal serial bus) Originally proposed by a consortium of Compaq, Digital, IBM, Intel, Microsoft, NEC and Northern Telecom (Nortel, now defunct) in March of 1995, it is now the standard computer serial connection. Hit the link for the latest versions.

Using The Internet For Seniors — Beginner's Guide [Anyone who names their website, "Cheeky Munkey" gets my support.]

USITT (United States Institute for Theatre Technology) The association of design, production, and technology professionals in the performing arts and entertainment industry.

USPTO (U.S. Patent & Trademark Office) Complete patent and trademark information is available free at this incredible website. Here you may search, read and print any U.S. patent granted since 1790 (really). [To download exact full-page patent images, complete with diagrams, requires you have a TIFF plug-in. All Internet US patents are in TIFF image file format, using CCITT Group 4 compression, as mandated by international standards. This requires third-party software to view these images either directly or after conversion to another format, such as Adobe PDF. A free, unlimited time TIFF plug-in offering full-size, unimpeded patent viewing and printing unimpeded by any advertising on Windows PCs is available from AlternaTIFF. Another useful site is US-Patent-Search.com: it is limited because you cannot do free searches, however if you know the patent number you can print the entire patent with one click, instead of having to print each page individually as required by the USPTO site].

universal time Abbr. UT The mean solar time for the meridian at Greenwich, England, used as a basis for calculating time throughout most of the world. Also called Greenwich time, Greenwich Mean Time, Zulu time. [AHD]

updater Someone who dates above their social status.

upfader A DJ term referring to the slider controlling the channel level. It is borrowed from stage lighting lingo meaning to bring up the lights, i.e., a lighting cue. The vertically mounted slide control normally moves from down (zero level) to up (maximum level), although these can be reversed in some DJ mixer designs. Contrast with crossfader.

up-tempo Music. A fast or lively tempo, as in jazz. [AHD]

UT See: universal time

UTP (unshielded twisted-pair) See cables.

UUT (unit under test) The entity to be tested. It may range from a simple diagnostic unit, or component, to a complete system. [IEEE]

UWB (ultrawideband) radio A type of wireless broadband radio that emits a broad spectrum of radio waves, potentially causing interference; also called impulse radio. FCC defines it as a bandwidth of at least 20% of the center frequency, or at least 500 MHz.

UV (ultraviolet) Electromagnetic radiation at frequencies higher than visible light yet lower than those of x-rays. Commonly used to erase EPROMs and in wireless and fiber optic data transmission.

uxoriousness 1. Excessively submissive or devoted to one's wife. 2. "A perverted affection that has strayed to one's own wife." — Ambrose Bierce.