Glossary of Audio Terminology

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Index | References




Haas Effect Also called the precedence effect, describes the human psychoacoustic phenomena for identifying the direction of a sound source heard from two directions 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 brain uses the time difference between these two arrivals to determine the direction in the horizontal plane of the sound source (localization in the vertical plane relies on subtle clues from the folds in the human ear).  Sound arriving at both ears simultaneously is heard as coming from straight ahead, or behind, or within the head.  The Haas Effect tells us that humans localize a sound source based upon the timing clues in the sound arriving over the first few Milliseconds of an acoustical event. If subsequent arrivals from different locations are within 10-35 milliseconds of the first, the later arrivals are integrated with and perceived as arriving form the location of the first arrival.  If the second arrival is longer than 35 milliseconds two distinct sounds (the original and a echo) are heard. The Haas Effect is occurs 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. (See Helmut Haas's doctorate dissertation presented to the University of Gottingen, Gottingen, Germany as "Über den Einfluss eines Einfachechos auf die Hörsamkeit von Sprache;" translated into English by Dr. Ing. K.P.R. Ehrenberg, Building Research Station, Watford, Herts., England Library Communication no. 363, December, 1949; reproduced in the United States as "The Influence of a Single Echo on the Audibility of Speech," J. Audio Eng. Soc., Vol. 20 (Mar. 1972), pp. 145-159.)

half-duplex Pertaining to a transmission over a circuit capable of transmitting in either direction, but only one direction at a time. See also: duplex

harmonic series 1. Mathematics. A series whose terms are in harmonic progression, as 1 + 1/3 + 1/5 + 1/7 + . . . 2. 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.

handshaking The initial exchange between two communications systems prior to and during transmission to ensure proper data transfer.

hard disk A sealed mass storage unit used for storing large amounts of digital data.

hard disk recording (HDR) See: DAW (digital audio workstation)

hardware The physical (mechanical, and electrical) devices that form a system. Separate and distinct from the software code or the program material.

hdCD (high density compact disc) See: DVD

HDCD (high definition compatible digital) Pacific Microsonics' trademark for their encode/decode scheme that allows up to 24 bit, 88.2 kHz digital audio mastering process, yet is compatible with normal 16 bit, 44.1 kHz CD and DAT formats. Claimed to sound superior even when not decoded, and to be indistinguishable from the original if decoded.

HDTV (high definition television) The standard for digital television in North America, still being revised.

Helmholtz, Hermann Ludwig Ferdinand von (1821-1894) German physicist and physiologist who formulated the mathematical law of the conservation of energy (1847) and invented an ophthalmoscope (1851) [An instrument for examining the interior structures of the eye, especially the retina, consisting essentially of a mirror that reflects light into the eye and a central hole through which the eye is examined. You aren't a real doctor without one!] Famous for his book, On the Sensations of Tone first published in 1862.

hertz Abbr. Hz. A unit of frequency equal to one cycle per second. [After Heinrich Rudolf Hertz.]

Hertz, Heinrich Rudolf (1857-1894) German physicist who was the first to produce radio waves artificially.

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. Each hexadecimal digit can be represented by a four-bit binary number.

Hi8 See: DA-88

high-pass filter A filter having a passband extending from some finite cutoff frequency (not zero) up to infinite frequency.

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."

HTML (hypertext markup language) The software language used on the Internet's World Wide Web (WWW). Used primarily to create web pages.

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.

hybrid A telecommunication 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). The name comes from the original use of a "hybrid coil" in the telephone whose function was to keep the send and receive signals separated. Both analog and digital hybrid designs are used.

hyperlink The protocol that allows connecting two Internet resources via a “link”; allowing the user a simple point-and-click method to move from viewing one resource to the next.

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.




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