O
1/4" TRS or 1/4" TS See connectors.
100Base-T or 1000Base-T See Ethernet.
1/f noise See flicker noise.
OAG (old analog guy) As opposed to a YDG.
object-oriented or object-based programming (Abbreviated OOP) A software technique in which a system program is expressed completely in terms of predefined things (objects), consisting of a set of variables and operations which can be performed on them, and the connections between objects.
oblique mode Acoustics. Sound reflecting between all six sides of a rectanguloid. Compare with tangential mode and axial mode.
ocarina Musical Instrument. A small terra-cotta or plastic wind instrument with finger holes, a mouthpiece, and an elongated ovoid shape. Named after Italian oca, goose, from the fact that its mouthpiece is shaped like a goose's beak. [AHD] Made famous when Bob Hope, Bing Crosby and Dorothy Lamour played ocarinas and sang the song, When the Sweet Potato Piper Plays in the movie Road to Singapore, in 1940. [Thanks GS!] And who can forget the ocarina solo in the soundtrack of The Good, The Bad, and the Ugly in 1967. See Ocarina History; also Viennese Vegetable Orchestra.
occlusion or occlusion effect Hearing. The phenomenon resulting from wearing solid earplugs, hearing aids or some personal monitors that makes the wearer's voice sound hollow and boomy to themselves, i.e., a voice-in-a-barrel effect. The earplugs block the ear canal resulting in a sound similar to sticking a finger in each ear and talking. This closure effect also produces louder sounds to the wearer since the ear canal blockage allows additional sound pressure to build up (rather than escape out the open ear canal) and be conducted to the inner ear. This is easily demonstrated by pronouncing and sustaining the word "fee," then sticking your fingers in your ears and notice how much louder it sounds (oh go ahead, no one is looking).
octal A number system using the base-8, i.e., each digit can be any of 8 values, represented by the digits 0-7. A three-bit binary number (since 23 = 8) can also represent each octal digit.
octaphonic or octophonic Multichannel Sound. Systems using eight discrete channels for recording and playback.
octave 1. Audio. The interval between any two frequencies having a ratio of 2 to 1. 2. Music a. The interval of eight diatonic degrees between two tones, one of which has twice as many vibrations per second as the other. b. A tone that is eight full tones above or below another given tone. c. An organ stop that produces tones an octave above those usually produced by the keys played. [AHD]
octet Music. a. The interval of eight diatonic degrees between two tones of the same name, the higher of which has twice as many vibrations per second as the lower. b. A tone that is eight diatonic degrees above or below another given tone. c. Two tones eight diatonic degrees apart that are sounded together. d. The consonance that results when two tones eight diatonic degrees apart are sounded. e. A series of tones included within this interval or the keys of an instrument that produce such a series. f. An organ stop that produces tones an octave above those usually produced by the keys played. g. The interval between any two frequencies having a ratio of 2 to 1. h. A music group consisting of eight members & instruments. [AHD] Computers. Eight bits, also called a byte.
Octopus Recording. The name given by comedian W.C. Fields for Les Paul's original Ampex 8-track Sel-Sync™ recorder.
octothorpe The "#" symbol on the telephone keypad, also known as a pound sign, crosshatch, number sign, sharp, hash, crunch, mesh, hex, flash, grid, pig-pen, gate, hak, oof, rake, fence, gate, grid, gridlet, square, and widget mark. Click the link to read the history of this creative word.
oersted Abbr. Oe The unit of magnetic field strength (intensity) in the centimeter-gram-second electromagnetic system, equal to the magnetic intensity one centimeter from a unit magnetic pole. [IEEE] Named after Hans Christian Oersted (1777-1851), Danish physicist. [AHD]
OFC (oxygen-free copper) Wire & Cables. Another of the popular audiophile myths that OFC power cables can improve sound. See Howard Johnson's wonderful essay titled: OFC madness: Facts, not fantasy, regarding power cables for high-end audio equipment.
off-axis response Any direction other than the on-axis response, i.e., the response measured along the imaginary straight line drawn through the geometric center of an object. In pro audio most often used in measurements of loudspeakers, microphones and humans.
Ogg Vorbis An open, royalty-free, pro audio encoding and streaming technology that competes with AAC, TwinVQ and other schemes. The name "Ogg" comes from a video game and "Vorbis" from a Terry Pratchett novel.
ohm Abbr. R or Greek upper-case omega, Ω A unit of electrical resistance equal to that of a conductor in which a current of one ampere is produced by a potential of one volt across its terminals. [After Georg Simon Ohm.]
Ohm, Georg Simon (1789-1854) German physicist noted for his contributions to mathematics, acoustics, and the measurement of electrical resistance. [AHD]
ohmage Misnomer. No such word. Bad, bad, really bad. Wrongful term for loudspeaker resistance. The correct term is impedance -- learn it; use it.
Ohm's Law The law stating that the direct current flowing in a conductor is directly proportional to the potential difference between its ends. It is usually formulated as V = IR, where V is the potential difference, or voltage, I is the current, and R is the resistance of the conductor. [After Georg Simon Ohm.] [Note: Georg Ohm did NOT formulate the basic power equations; that was done by James Joule: see Joule's Law.]
OIART (Ontario Institute of Audio Recording Technology) This Canadian school offers a three-term, forty-six week immersion course designed to prepare graduates for a career in the professional audio recording and audio communications industry.
OLED (organic light emitting diode) A type of LED display made from organic polymers (think plastic that glows) that provides a wide viewing angle and uses low power. OLED displays do not require a backlight as do LCD screens. OLED screens can also be fabricated on plastic as well as glass substrates, making them more flexible and durable. See OLED for details.
OL light See overload light.
Olson, Harry Ferdinand, Ph.D. (1901-1982) American engineer who worked 40 years at RCA labs, recognized and honored as a pioneer and leading authority in acoustics and electronic sound recording. He was granted over 100 patents, along with many awards and medals for his contributions to the science of sound. He authored more than 130 technical papers and wrote several textbooks still considered the best of their genre.
omnidirectional microphone One with a response pattern that is as close to a perfect sphere as possible. Receives sound from all directions equally well. Compare with unidirectional mic and cardioid microphone.
on-axis response See off-axis response.
Ondes-Martenot Synthesizers. (oenz MAR-te-noe) - An early synthesizer from 1928. A monophonic theremin-sounding (link) instrument using a stretched wire under a keyboard with timbre and loudness controls. It was the female voice effect in the original Star Trek TV theme.
one-bit data converter Loose reference to any of the various data conversion schemes (e.g., delta-sigma, adaptive delta modulation, etc.) that use only one binary bit (i.e., levels 1 and 0) in the conversion and storage process.
one-third octave 1. Term referring to frequencies spaced every one-third of an octave apart. One-third of an octave represents a frequency 1.26-times above a reference, or 0.794-times below the same reference. The math goes like this: 1/3-octave = 21/3 = 1.260; and the reciprocal, 1/1.260 = 0.794. Therefore, for example, a frequency 1/3-octave above a 1 kHz reference equals 1.26 kHz (which is rounded-off to the ANSI-ISO preferred frequency of "1.25 kHz" for equalizers and analyzers), while a frequency 1/3-octave below 1 kHz equals 794 Hz (labeled "800 Hz"). Mathematically it is significant to note that, to a very close degree, 21/3 equals 101/10 (1.2599 vs. 1.2589). This bit of natural niceness allows the same frequency divisions to be used to divide and mark an octave into one-thirds and a decade into one-tenths. 2. Term used to express the bandwidth of equalizers and other filters that are 1/3-octave wide at their -3 dB (half-power) points. 3. Approximates the smallest region (bandwidth) humans reliably detect change. See critical bands. Compare with third-octave.
onomastics 1. a. The study of the origins and forms of proper names. b. The study of the origins and forms of terms used in specialized fields. 2. The system that underlies the formation and use of proper names or terms used in specialized fields. [AHD]
onomatopoetic The formation or use of words such as buzz, hiss, splash, sizzle or murmur that imitate the sounds associated with the objects or actions they refer to. [AHD] See zaa zaa.
OOP See object-oriented.
op amp (operational amplifier) An analog integrated circuit device characterized as having two opposite polarity inputs and one output, used as the basic building block in analog signal processing. See vacuum-tube op amps.
open circuit Electronics. The condition where there is no connection between two nodes, resulting in zero current flow between the nodes. Electricity. Containing a gap across which electricity cannot pass: an open circuit.[AHD]
opera 1. A theatrical presentation in which a dramatic performance is set to music. [AHD] 2. "I do not mind what language an opera is sung in so long as it is a language I don't understand". Edward Appleton, Observer August 28, 1955. [Crystal] 3. "An unalterable and unquestioned law of the musical world required that the German text of French operas sung by Swedish artists should be translated into Italian for the clearer understanding of the English-speaking audiences". Edith Wharton, 1920, The Age of Innocence. [Crystal]
optical-fiber cable See fiber-optics.
optocoupler Any device that functions as an electrical-to-optical or optical-to-electrical transducer.
OR Computer Science & Logic. A Boolean logical operator that returns a true value if one or both operators are true; a form of addition. For example, two parallel connected switches, A and B, requires one or both be closed for current to pass, thus it requires switch A OR switch B closed to operate.
orange One of the words in the English language without a rhyme -- some others are "month," "purple," and "silver."
orange noise See noise color.
ordinate Mathematics. The plane Cartesian coordinate representing the distance from a specified point to the x-axis, measured parallel to the y-axis. [AHD]
organ Music. 1. An instrument consisting of a number of pipes that sound tones when supplied with air and a keyboard that operates a mechanism controlling the flow of air to the pipes. Also called pipe organ. 2. Any one of various other instruments, such as the electronic organ, that resemble a pipe organ either in mechanism or sound. [AHD]
organic LED See OLED.
organ of Corti Hearing. A specialized structure located on the inner surface of the basilar membrane of the cochlea containing hair cells that transmit sound vibrations to the nerve fibers. [AHD]
oronyms Speech. Streams of sound than can be carved into words in two different ways, i.e., it illustrates the seamlessness of speech. For example oronyms are often found in songs and nursery rhymes such as the famous "Mairzey doats and dozey doats, And little lamsey divey, A kiddley-divey do, Wouldn't you?" From Pinker.
orotund 1. Pompous and bombastic: orotund talk. 2. Full in sound; sonorous: orotund tones. [AHD]
ORTF (Office de Radiodiffusion -- Television Francaise) An initialism formed from the name of the French national broadcasting system, who designed a stereo microphone recording technique known as the ORTF method. The technique uses two cardioid microphones with a spacing of 17 cm between the microphone diaphragms, and with an 110° angle between the capsules. This technique reproduces stereo cues similar to those used by the human ear to perceive directional information in the horizontal plane. The spacing of the microphones emulates the distance between the human ears, and the angle between the two directional microphones emulates the shadow effect of the human head. The ORTF stereo technique provides the recording with a wider stereo image than X-Y stereo while still preserving good mono information.
orthogonal 1. Relating to or composed of right angles. 2. Mathematics. a. Of or relating to a matrix whose transpose equals its inverse. b. Of or relating to a linear transformation that preserves the length of vectors.
oscillator Electronics & Synthesizers. A circuit that continuously alternates between two (or more) states [IEEE]; the period between alternations defines the frequency of oscillation. A common said complaint of electronic engineering students is that they build "amplifiers that oscillate and oscillators that amplify".
oscilloscope Electronic Test Equipment. An instrument primarily for making visible the instantaneous value of one or more rapidly varying electrical quantities (typically voltage) as a function of time or another electrical or mechanical quantity. [IEEE]
OSD (on-screen display) chip An integrated circuit providing all necessary functions for adding text to television or video monitor display screens.
OSI (open system interconnection) The only internationally accepted framework of standards for communication between different systems made by different vendors. The model originally developed by ISO describing computer communication services and protocols without making assumptions concerning language, operating systems or application issues. The main goal is to create an open systems networking environment where any vendor's computer system, connected to any network, can freely share data with any other computer system on that network See The 7 Layers of the OSI Model.
ostinato Music. A short melody or pattern that is constantly repeated, usually in the same part at the same pitch. [AHD]
OTPROM (one-time programmable read-only memory) A redundant term, incorrectly used to mean PROM -- a PROM, by definition, is a one-time device.
outboard unit External, usually referring to a separate piece of signal processing gear located remote to a mixer that connects in the effects loop.
out-of-phase In an un-synchronized or un-correlated way. See polarity and phase et al.
output impedance Electronics. The output driving impedance of a device, usually low in the 50-300 ohm range. Output impedance is frequency dependent and varies as a function of circuit feedback, therefore the value given must state the frequency range it covers.
overdub Recording. To add (supplementary recorded sound) to a previously taped musical recording especially in order to heighten the total effect. Additional recorded sound that is blended into a musical recording. [AHD] Usually done while listening to the previously recorded music on the same tape recorder or device.
overload light or OL light An indicator found on pro audio signal processing units that lights once the signal level exceeds a preset point. There is no standard specifying when an OL light should illuminate, although common practice makes it 3-4 dB below actual clipping. Good signal processing design ensures that the OL light illuminates anytime the signal exceeds the set point, anywhere in the signal path, not just the input or output level.
overs A term associated with A/D converters used to describe input signals exceeding the full scale range (0 dBFS). Overs indicators vary from simple single LEDs to elaborate calibrated digital meters. To be of genuine value the overs indicator, however displayed, must be based on reading the true digital code associated with the input level. It is important to distinguish between 0 dBFS and overs; they are not the same. 0 dBFS is the absolute highest voltage level that any particular A/D can convert. It produces the equivalent of a digital code consisting of all 1s. No digital level can exceed 0 dBFS. A 0 dBFS voltage level and all levels greater than this produce the same output code of all 1s. A true overs indicator actually counts the number of times that the 0 dBFS level was exceeded and displays this number. As yet there is no standard as to how many samples exceeding 0 dBFS constitutes an over. Everyone agrees that very brief excursions beyond 0 dBFS (producing digital clipping) cannot be heard; however no such agreement exists as to just how many samples it takes before an over is audible.
oversampling 1. Sampling at a rate higher than the sampling Nyquist theorem. 2. A technique where each sample from the data converter is sampled more than once, i.e., oversampled. This multiplication of samples permits digital filtering of the signal, thus reducing the need for sharp analog filters to control aliasing. See the RaneNote Digital Dharma of Audio A/D Converters.
overtone Same as harmonic.
Oz From Frank Baum's "The Wizard of Oz," the name was created when he looked at his filing cabinet and saw "A-N," and "O-Z," hence "Oz."
