Dictionary of Audio Terminology - H
H - The symbol for henry, a measure of inductance.
Haas Effect - Also called the precedence effect, describes the human psychoacoustic phenomena of correctly identifying the direction of a sound source heard in both ears but arriving at different times. Due to the head's geometry (two ears spaced apart, separated by a barrier) the direct sound from any source first enters the ear closest to the source, then the ear farthest away. The Haas Effect tells us that humans localize a sound source based upon the first arriving sound, if the subsequent arrivals are within 25-35 milliseconds. If the later arrivals are longer than this, then two distinct sounds are heard. The Haas Effect is true even when the second arrival is louder than the first (even by as much as 10 dB.). In essence we do not "hear" the delayed sound. This is the hearing example of human sensory inhibition that applies to all our senses. Sensory inhibition describes the phenomena where the response to a first stimulus causes the response to a second stimulus to be inhibited, i.e., sound first entering one ear cause us to "not hear" the delayed sound entering into the other ear (within the 35 milliseconds time window). Sound arriving at both ears simultaneously is heard as coming from straight ahead, or behind, or within the head. The Haas Effect describes how full stereophonic reproduction from only two loudspeakers is possible.
habanera – (1) A slow Cuban dance. (2) The music for this dance, in duple time. [AHD]
Hafler, David - (b. 1919-2003) American engineer, inventor and member of the Audio Hall of Fame, considered one of the fathers of high fidelity. He founded Acrosound (1950), Dynaco (1954) and the David Hafler Company (1972).
half-duplex - Pertaining to a transmission over a circuit capable of transmitting in either direction, but only one direction at a time.
half-normalled - where only one of the insert points (top: send, or bottom: receive) breaks the signal path (in normalling
half-step or half-tone - (1) A marching step of 15 inches (38 centimeters) at quick time and 18 inches (46 centimeters) at double time. [AHD] (2) A pitch change equivalent to that produced by two adjacent piano keys. A semitone.
half-wave rectification - Term used to describe a rectifier that passes only one-half of each incoming sinusoid, and does not pass the opposite half-cycle. [IEEE]
Hall effect or Hall voltage - In a semiconductor, the Hall voltage is generated by the effect of an external magnetic field acting perpendicularly to the direction of the current.
Hall, Edwin Herbert - (1855-1938) American physicist best known for his 1879 discovery of the Hall effect.
Hammond, Laurens (b. 1895-1973) American engineer/inventor/founder of the Hammond Organ company in 1935 and developer of the spring reverb based on a Bell Labs invention.
Hamster switch - A control found on professional DJ performance mixers that reverses fader action. For example, if a fader normally is off at the bottom of its travel and on at the top of its travel, then activating the hamster switch reverses this, so off is now at the top and on is at the bottom of travel, or alternatively, it swaps left for right in horizontally mounted faders.
Handshaking - The initial exchange between two communications systems prior to and during transmission to ensure proper data transfer.
Hanley, Bill - Known as the father of festival sound and is recognized by his fellow professionals as a technical innovator, he is best known for helping to create the Newport Jazz Festival, and for engineering the greatest concert of the 20th Century, the Woodstock Music and Art Fair in August of 1969.
haptic - Of or relating to the sense of touch; tactile. [AHD]
hard clipping - term used to describe extreme clipping of a signal, producing highly visible flattoped waveforms as viewed on an oscilloscope.
hard disk - A sealed mass storage unit used for storing large amounts of digital data.
hard disk recording – (1) An audio recording device based on computer hard disk memory technology. Typically, these machines are configured like analog tape recorders offering 24-48 tracks, utilizing 24-bit / 48-96 kHz data converters with optional I/O to interface with ADAT, TDIF, or AES3, and file format interchangeability with DAWs. (2) Any of several software/hardware systems using a computer as the basis for creating, editing, storing, and playback of digital audio, using the computer's hard disk as the recording medium, or a SAN.
hard-drawn copper wire - Soft, annealed copper wire drawn through a series of dies in order to increase its tensile strength. The hard drawn copper wire was strong enough for overhead wires and copper replaced iron for the telephone market.
Hardware - The physical (mechanical, and electrical) devices that form a system.
hardware key - Security device for protected software: a small hardware device that, when plugged into a computer, enables a specific copy-protected program to run, the program being disabled on that computer if the device is not present. The device is effective against software piracy.
Harman, Sidney - (b. 1918-2011) Pro audio industry icon and Chairman Emeritus of Harman International Industries.
harmonic – (1) Any of a series of musical tones whose frequencies are integral multiples of the frequency of a fundamental tone. (2) A tone produced on a stringed instrument by lightly touching an open or stopped vibrating string at a given fraction of its length so that both segments vibrate. Also called overtone, partial, partial tone.
harmonic distortion - A true THD measurement consists of a computation from a series of individual harmonic amplitude measurements, rather than a single measurement. "THD" is the square root of the sum of the squares of the individual harmonic amplitudes. And the answer must specify the highest order harmonic included in the computations; for example, "THD through 8th harmonic." [from Metzler]
harmonicity - The degree to which a sound's timbre conforms to a harmonic series.
harmonic overtones - Any frequency higher than the fundamental frequency of a sound.
harmonic series – (1) In reference to mathematics, a series whose terms are in harmonic progression, such as 1 + 1/2 + 1/3 + 1/4 + 1/5 + ...
(2) In reference to music, a series of tones consisting of a fundamental tone and the overtones produced by it, and whose frequencies are consecutive integral multiples of the frequency of the fundamental. [AHD]
harmonic telegraph - The original name given by Alexander Graham Bell to his idea that the telegraph could be used to transmit sound.
Harmonizer® - Registered trademark of Eventide for their pitch-shifting signal processing product line.
Harrison, David - (b. 1942-1995) American musician and engineer who founded Harrison Consoles. He pioneered the modern "in-line" audio console in 1970, licensing his first design to MCI who sold it as the MCI 400.
Harrison, Ercel B. - American engineer who was the chief designer at Peerless Transformers, where he designed the first full frequency transformers for the motion picture industry. He is regarded as a legend of transformer design and innovation.
harrumph - To make a show of clearing one's throat. [AHD]
Harvard sentences - IEEE standard recommended sentences for measuring speech quality.
HATS (head and torso simulator) - A dummy head, with artificial ears and ear canals fitted with microphones, and a torso, used to measure acoustic parameters.
HAVi (Home Audio/Video interoperability) - An industry standard for home networks designed to link consumer electronics products. Developed by eight consumer giants -- Grundig, Hitachi, Panasonic, Philips, Sharp, Sony, Thomson Multimedia and Toshiba -- the main aim of this protocol is to ride on IEEE 1394 interface, connecting digital TVs, set-top boxes, DVD players and other digital consumer products.
HDBaseT Abbr. HDBT - A multimedia connectivity standard optimized for full uncompressed HD video, audio, 100Base-T Ethernet, power over cable and various control signals through a single Cat 5e cable.
hdCD (high density compact disc) - Officially "DVD" does not stand for anything. It used to mean "digital versatile disc" -- and before that it meant "digital video disc" also once known as hdCD in Europe.
HDCD (high definition compatible digital) - Pacific Microsonics' (now owned by Microsoft) trademark for their encode/decode scheme that allows up to 24 bit, 176.4 kHz digital audio mastering process, yet is compatible with normal 16 bit, 44.1 kHz CD and DAT formats.
HDR (hard-disk recorder) - An audio recording device based on computer hard disk memory technology. Typically, these machines are configured like analog tape recorders offering 24-48 tracks, utilizing 24-bit / 48-96 kHz data converters with optional I/O to interface with ADAT, TDIF, or AES3, and file format interchangeability with DAWs.
HD Radio - Formerly called IBOC, the digital radio technology that allows simultaneous broadcasting of analog and digital signals using present radio spectrum allocations.
HDTV (high definition television) - The standard for digital television in North America, still being revised. When finished will include a definition for picture quality at least that of a movie theater, or 35 mm slide, i.e., at least two million pixels (compared to 336,000 pixels for NTSC).
head amp – In reference to electronics (1) A pre-preamplifier or simply a preamplifier. A very low noise, high gain audio preamp used to boost signal levels from very low sources such as moving coil phono cartridges, some acoustic pick-ups, etc. (2) Slang for headphone amplifier. (3) A guitar amplifier without speakers that usually sits on top of and forms the "head" of a loudspeaker stack, classically comprised of two cabinets consisting of four 10" or 12" drivers each.
headphones - An electromagnetic transducer usually based on the principle of electromagnetic induction used to convert the electrical energy output of a headphone amplifier into acoustic energy.
headphone sensitivity - The standard is to apply one milliwatt and then measure the sound pressure level at the earpiece (using a dummy head with built-in microphones). [IEC 60268-7].
headroom - A term related to dynamic range, used to express in dB, the level between the typical operating level and the maximum operating level (onset of clipping).
headshell - The removable part of the cartridge mounting assembly attached to the end of the turntable arm.
HeadWize A non-profit site specializing in headphones and headphone listening, featuring articles, essays, projects and technical papers on all things headphone -- very informative.
H.E.A.R. (Hearing Education and Awareness for Rockers) - A non-profit volunteer organization dedicated to raising awareness of the real dangers of repeated exposure to excessive noise levels from music which can lead to permanent, and sometimes debilitating, hearing loss and tinnitus.
hearing - Perceiving sound by the ear. [AHD]
hearing loop (aka inductive loop) -A thin copper wire surrounding an area that transmits audio wirelessly to standard hearing aids and cochlear implants, so equipped.
heat sink - A protective device that absorbs and dissipates the excess heat generated by a system. [AHD] Generally a mass of metal (usually aluminum) having much greater thermal capacity than the attached heat source.
Heaviside, Oliver - (b. 1850-1925) British self-taught engineer, mathematician and physicist, a giant among giants who independently discovered Laplace-like operatives used to simplify differential equations and co-invented vector analysis which he used to reformulate Maxwell's equations (from twenty equations to the famous four of today).
heavy-metal - A form of rock music characterized by extreme volume, high-intensity electric guitar, flashy costumes and dramatic stage performances. Originally coined by William Burroughs in his book, Naked Lunch, it was first voiced in music, "heavy-metal thunder," in Steppenwolf's "Born to be Wild." The song believed to be the first heavy-metal piece was a remake of Eddie Cochran's "Summertime Blues" recorded by Blue Cheer in 1968.
hecto- or hect- - Prefix meaning one hundred (10²)
hectometer Abbr. hm - A metric unit of length equal to 100 meters. [AHD]
HEI (House Ear Institute) - Established in 1946, a private nonprofit organization, with an international reputation as a leader in its field through its applied otologic research and education programs.
Heil, Oskar - (b. 1908-1994) German electrical engineer and inventor famous in pro audio for his invention of the air motion transformer loudspeaker.
Heinrich - The first disco dance club is said to be the Scotch Club in Aachen, Germany with the first disco DJ being Heinrich (real name: Klaus Quirini) who started it all in October 1959.
Heisenberg, Werner Karl - (b. 1901-1976) German physicist and a founder of quantum mechanics. He won a 1932 Nobel Prize for his uncertainty principle.
Heisenberg uncertainty principle - "The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa." -- Heisenberg, uncertainty paper, 1927.
Helmholtz Equation - Used in acoustics and electromagnetic studies. It arises, for example, in the analysis of vibrating membranes, such as the head of a drum, or in solving for room modes.
Helmholtz, Hermann Ludwig Ferdinand von - (b. 1821-1894) German physicist and physiologist who formulated the mathematical law of the conservation of energy (1847) and invented an ophthalmoscope (1851) [AHD]
Helmholtz resonator - the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle. The name comes from a device created in the 1850s by Hermann von Helmholtz, the "Helmholtz resonator", which he, the author of the classic study of acoustic science, used to identify the various frequencies or musical pitches present in music and other complex sounds. [Wikipedia]
Hellertion - An early synthesizer from 1928. A monophonic instrument using four leather touchtone fingerboards.
henry Abbr. H - The unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. [After Joseph Henry.] [AHD]
Henry, Joseph - (b. 1797-1878) American physicist who performed extensive studies of electromagnetic phenomena. [AHD]
hertz Abbr. Hz - A unit of frequency equal to one cycle per second (cps). [After Heinrich Rudolf Hertz.]
Hertz, Heinrich Rudolf - (b. 1857-1894) German physicist who was the first to produce radio waves artificially. [AHD]
heterodyne - Having alternating currents of two different frequencies that are combined to produce two new frequencies, the sum and difference of the original frequencies, either of which may be used in radio or television receivers by proper tuning or filtering. [AHD]
heuristic - Relating to or using a problem-solving technique in which the most appropriate solution of several found by alternative methods is selected at successive stages of a program for use in the next step of the program. [AHD]
hexadecimal - A number system using the base-16, i.e., each number can be any of 16 values. Normally represented by the digits 0-9, plus the alpha characters A-F. A four-bit binary number can represent each hexadecimal digit.
Heyser, Richard C. - (b. 1931-1987) American engineer best known to the pro audio world for his pioneering work with time delay spectrometry (TDS).
HF (high frequency) - 3 MHz to 30 MHz
H(ermon) H(osmer) Scott - (b. 1909-1979) American engineer most famous for his very successful and important contributions to consumer hi-fi systems.
Hi8 - Sony-developed "Hi8" 8mm videotape as the storage medium.
hichiriki - A type of Japanese flute.
hide - A set of drums. [Decharne]
high-cut filter also hi-cut 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.
high impedance Abbr. Hi-Z - A device having an electrical impedance of at least 2,000 ohms. [Note: This value is arbitrary as there is no standard defining exactly what constitutes a 'high impedance.']
highlife - Popular West African dance music that combines African rhythms and Western-style pop melodies.
high-pass filter also hi-pass filter - A filter having a passband extending from some finite cutoff frequency (not zero) up to infinite frequency. An infrasonic filter is a high-pass filter.
Hilliard, John Kenneth - (b. 1901-1989) American physicist and distinguished acoustical engineer who began his career pioneering audio soundtracks for movies.
Hi-NRG (High Energy) - From the Evelyn Thomas disco hit, "High Energy." A form of electronic dance music popular in the '80s.
hip-hop - A musical genre term whose origin is still debated, but most credit Afrika Bambaataa and the Zulu Nation who used the term in the late '70s to describe their South Bronx block parties.
hiss - Random high frequency noise with a sibilant quality, most often associated with tape recordings. In reference to acoustics, a term for noise in the 2 kHz to 8 kHz range.
History of Concert Sound - Great repository of concert sound history created by Doug Fowler.
Hi-Z (high impedance) - A device having an electrical impedance of at least 2,000 ohms. [Note: This value is arbitrary as there is no standard defining exactly what constitutes a 'high impedance.'] Examples include headphones rated 600 ohms and up (headphone division between hi-Z and lo-Z is lower than other devices); microphones rated 10k - 100k ohms; and most circuit inputs are high-impedance, rated at 2k-100k ohms.
holodigital square - Square number containing each decimal digit exactly once, e.g., 9,814,072,356 is the largest example (i.e., 99,0662).
Holophonics - An acoustical recording and broadcast technology claimed to be the aural equivalent to holography, hence the name. Holophonics is an encode process that occurs during the recording session using a special listening device named "Ringo." It is claimed that "playback or broadcast is possible over headphones or any existing mono or stereo speaker system, with various levels of spatial effect. Optimal effects occurs when two tracks (stereo) are played utilizing digital technology over headphones and minimal effect when played over a single mono speaker (two tracks merged into one and played over a single speaker)."
HomeRF Lite - A low-cost, low-power, two-way, wireless communications standard between compliant devices anywhere in and around the home (automation, toys, PC peripherals, etc.), developed by Philips and others. Claiming lower cost, lower power consumption, higher density of nodes per network and simplicity of protocols, it is an alternative to Bluetooth.
horn - A sound radiator cone mounted onto a loudspeaker diaphragm to amplify its output based on the same principal found in musical instrument horns.
Horner, William George - (b. 1786-1837) English mathematician and inventor of the Zoetrope.
horse-head fiddle or morin khuur - Mongolian horse-headed violin.
horsepower Abbr. hp - A unit of power in the U.S. Customary System, equal to 745.7 watts or 33,000 foot-pounds per minute (550 foot-pounds per second). [AHD]
hot water Running hot water has a lower pitch than running cold water.
hour Abbr. h - One of the 24 equal parts of a day. [AHD]
hourglass drum - Drum design featuring drumheads attached by laces that are squeezed to change the pitch. Many variations and regional names exist.
house curve - The name given to the weighting, or alteration, of the sound equalization for a room. It is a rule-of-thumb for what to do after achieving the flattest possible response. Different venues require different house curves with wide variation between many favorites. The most common one is for speech reinforcement in large auditoriums (only) and measures 10 dB down at 10 kHz with respect to 1 kHz (this is a 3 dB/octave slope). This contrasts to the 2 -3 dB used in many small control rooms. The proper choice is heavily dependent on the source material (speech vs. music) and the venue (large vs small; reverberant or dry); there is no one standard.
House Ear Institute or HEI - Established in 1946, a private nonprofit organization, with an international reputation as a leader in its field through its applied otologic research and education programs.
house mixer - Used to describe the main mixer usually located in the audience for sound reinforcement systems. Meant to differentiate the main house mixer from the monitor mixer normally located to the side of the stage.
house sync - A distributed master signal used to guarantee all digital devices run at the same speed. Hit the link for details.
HOW (house of worship) - Generic term for any structure used for religious gathering, includes churches, synagogues, temples and mosques; a sacred space.
howlround - What the British call acoustic feedback.
H-PAS (Hybrid Pressure Acceleration System) - A proprietary loudspeaker technology licensed Atlantic Technology, in collaboration with Solus/Clements Loudspeakers, based on a concept developed by Philip R. Clements circa 1979 (U.S. patent 4,373,606, Loudspeaker enclosure and process for generating sound radiation, granted on February 15, 1983). Not relying on electronics, this bass extending idea uses a specially designed chamber to acoustically amplify low frequencies, e.g., a -3dB point of 28 Hz for a single 5 1/4" driver is achievable.
HRMAI (high-resolution multichannel audio interconnection) - From AES standard AES50: AES Standard for digital audio engineering -- High-resolution multichannel audio interconnection (HRMAI). "A high- performance point-to-point audio interconnection rather than a network, although the auxiliary data may operate as a true network, independently of the audio."
HRRC (Home Recording Rights Coalition) - An advocacy group that includes consumers, retailers, manufacturers and professional servicers of consumer electronics recording products.
HRTF (head-related transfer function) - The impulse response from a sound source to the eardrum is called the head-related impulse response (HRIR), and its Fourier transform is called the head-related transfer function (HRTF). The HRTF captures all of the physical cues to source localization, and is a surprisingly complicated function of four variables: three space coordinates (azimuth, elevation & range) and frequency, and to make matters worst, they change from person to person. Interaural (i.e., between the ears) time differences, interaural time delays and the physical effects of diffraction of sound waves by the torso, shoulders, head and pinnae modify the spectrum of the sound that reaches the eardrums. These changes allow us to localize sound images in 3D space and are captured by the HRTFs. HRTFs have been named and studied since at least the early '70s [Blauert]
HTML (hypertext markup language) The software language used on the Internet's World Wide Web (WWW). Used primarily to create home pages containing hypertext.
HTTP (hypertext transfer protocol) - The name for the protocol that moves documents around the Internet/Web. Used by the various servers and browsers to communicate over the net.
hub - (1) In broadband LAN use, a central location of a network that connects network nodes through spokes, usually in a star architecture. Think of it as a digital splitter, or distribution amplifier. (2) In complex systems, hubs perform the basic functions of restoring signal amplitude and timing, collision detection and notification, and signal broadcast to lower-level hubs.
hubbub - Loud, confused, or disagreeable sound or sounds that emphasizes turbulent activity and concomitant din. [AHD]
Huffman coding or Huffman algorithm - One of the MP3 and AAC techniques used in digital audio data compression. While not a compression technique in itself, it is used in the final steps to code the process, and is an ideal complement of the perceptual coding. Huffman codes are used in nearly every application that involves the compression and transmission of digital data, such as fax machines, modems, computer networks, and high-definition television.
Hullabaloo - Great noise or excitement; uproar; disorderly tumult together with loud, bewildering sound. The lagging of an effect behind its cause, as when the change in magnetism of a body lags behind changes in the magnetic field.
Humanthesizer - Hit the link to read & see performance artist Calvin Harris take MIDI to a new extreme as created by Phil Clandillon and Steve Milbourne of Sony/BMG.
humbucking pickup - A pickup arrangement usually found on electric guitars designed to reduce the effects of 50 Hz or 60 Hz hum products. Typically this is done using two pickups wired electrically and magnetically opposite so as to cancel (buck) induced hum and other noise interference. Invented by engineer Seth Lover at Gibson and patented as US 2,896,491 granted in 1959 but filed in 1955, and first appeared on Gibson steel guitars in 1956 and then on the legendary Les Paul models beginning in 1957. Leo Fender received his humbucking pickup patent, US 2,817,261 in 1957 after filing in 1956.
hum components - The harmonics of the AC mains supply. The Americas (except the southern half of South America), Japan, Taiwan, Korea and the Philippines use a 60-Hz system, placing the most annoying 2nd and 3rd harmonics at 120 Hz and 180 Hz. For Europe, and the rest of the world using 50-Hz mains, these components fall at 100 Hz and 150 Hz.
huqin - Chinese bowed string instruments.
hurdy-gurdy – (1) A medieval stringed instrument played by turning a rosined wheel with a crank and depressing keys connected to tangents on the strings. (2) Any instrument, such as a barrel organ, played by turning a crank. [AHD]
HVAC - Term used to stand for the heating, ventilating, & air conditioning system of any building. Electrical engineering. Term used to mean high-voltage alternating current.
hybrid - In reference to telecommunications, a term used to describe an interface box that converts a conversation (or data signal) coming in on two pairs (one pair for each direction of the conversation or signal) onto one pair and vice versa (i.e., a 2-wire to 4-wire converter).
hybrid shield termination - The name for the termination technique where the shield is bonded to the sending end's metal chassis and is capacitively-coupled to the receiving end's metal chassis.
hydrophilic - Having an affinity for water; readily absorbing or dissolving in water. [AHD]
hydrophone - An electrical instrument for detecting or monitoring sound under water. [AHD]
hypercardioid microphone – Similar to the polar pattern of a cardioid microphone but with a tighter area of front sensitivity and a smaller lobe of rear sensitivity.
hyperlink - The protocol that allows connecting two Internet resources via a single word or phrase; allowing the user a simple point-and-click method to create the link.
HyperPhysics - A website concept created by Carl R. (Rod) Nave, Department of Physics and Astronomy, Georgia State University.
hypersonic sound - Term that describes the emerging audio technology of using wireless ultrasonic signals and nonlinear signal mixing techniques to produce sound located only in very specific areas.
hypertext - Within WWW documents, the linking of words to other sections of text, pictures or sound is called hypertext. Hypertext is created using the HTML software language. Also used frequently in Help files.
hysteresis - The lagging of an effect behind its cause, as when the change in magnetism of a body lags behind changes in the magnetic field. [AHD] The maximum difference in value for a digitizer code transition level when the transition level is approached from either side of the transition. [IEEE]
Hz or hertz - A unit of frequency equal to one cycle per second (cps).
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