Haas Effect, Precedence Effect@An audio perception phenomenon, where duplicate versions of a sound source arrive from two separate locations, one delayed in time with respect to the other. The listener will "Localize" the sound towards the source which arrives first. That is to say, sounds seem to come from the direction from which they arrived first. The degree to which the Haas Effect will influence our perception of the localization of sound sources is also affected by the actual amount of delay between the two sounds, their respective levels, and the nature of the sounds themselves. Knowledge of this phenomenon can be of great use when configuring delays during a stereo or surround mixdow. It is also a critical issue when placing loudspeakers for sound reinforcement over long distances. (Speakers distant from the direct source, or stage speaker, may need to be delayed in order to maintain correct localization of the sound source at its acoustic point of origin. In addition, arrival time differences greater than 30 milleseconds greatly deteriorate speech intelligibility.). See also Psychoacoustics.@Hacker@Originally, person who can do "quick and dirty" programming, a "hack" job that achieves a short-term solution (such as might be done by a "hack" author or performer, a drudge or ungraceful practitioner of the art). Popular use of the term has come to mean any person adept at using computer programs, particularly people who make custom modifications to a program or computer system, for their own fiendish purposes. In the mass media, "hacker" is often used with the following connotations: 1) individuals who create computer viruses, or 2) a person who attempts to breach the security measures which control access to computer systems.@Half-Normalled Patchbay@Half-Normalled patchbays have each rear-panel input routed to the corresponding rear-panel output. Plugging a cable into the lower front jack breaks this normalled connection, while connecting an audio source to the upper front input ONLY will route this signal to both the front and rear panel outputs for this position. Half-Normalled connections provide a convenient way of splitting a signal (a "Mult"); the signal still continues to its normal destination, but also is routed to an additional output. See also Normalled-Patchbay, Patchbay.@Hard Drive, Hard Disk, Fixed Disk@A large-capacity disk storage system for computers. Multiple disk platters are stacked on a common spindle within a sealed enclosure. Individual read/write heads float above the surface of each platter, which is coated with a magnetic oxide. All heads are mounted on a common armature known as a head actuator, whose movement is controlled by a solenoid. The entire disk mechanism appears as a single disk "volume" to the computer. Data is written magnetically onto the platters, in concentric data tracks each corresponding to one full disk revolution underneath the read/write head; a data "cylinder" represents the sum of the data provided by the same track on all platters. Rotational speeds of 3600 to 7200 r.p.m. are common. "Internal" hard drives (mounted within a computer) can share its power supply, while external drives must incorporate their own, making them slightly more expensive. See also SCSI.@Hardware@The actual mechanical and electrical components that comprise an electronic or computer system, versus the instructions, or programs, that are loaded into a microchip-controlled system such as a computer (the software).@Hardwired@A permanent hardware connection, which cannot be changed or re-routed by the user. The term is also used figuratively to refer to similar situations within computer software, where the program or operating system does not permit altering the routing of data or other signals.@Harmonics, Partials, Overtones@Part of the frequency structure of complex waveforms, which contributes to their unique timbre. Partials are all frequencies present in a sound, other than the Fundamental (the principal tone perceived by the listener, usually the lowest frequency). All Partial tones whose frequency is higher than the fundamental are referred to as Overtones. Harmonics are a specific class of Overtones, at frequencies which correspond to integer multiples of the tone's Fundamental frequency (actually, the first harmonic is the fundamental itself, so the first overtone is the second harmonic!). Harmonics correspond to partial modes of vibration, symmetrical divisions of the length of a string or vibrating air column. The amplitudes (loudness) of successive ascending harmonics decreases in proportion to their integer multiple of the fundamental. This sequence of frequencies at integer multiples above a fundamental musical tone (1f, 2f, 3f, 4f, 5f, etc.), is called a Harmonic Series; it is characteristic of the overtone structure on all string and wind instruments. See also Fundamental.@Harmonize@A specialized type of Pitch Shifting (an audio processor which applies a specified transposition interval to the input signal, usually defined in musical semitones and/or cents). In "harmonizing" pitch shifters the actual amount of pitch shift, with respect to the input tone's fundamental, is adjusted up or down to conform to the steps of a specified musical scale, rather than maintaining a constant, parallel interval to the input tone. For example, an ascending melody can be harmonized in "thirds"; the pitch-shifted harmony produced by the processor for each incoming note will be automatically adjusted to either a major or minor third, as appropriate, to stay within a musical scale specified by the user. "Harmonizer" is a trademark of Eventide, the company that pioneered this signal processing technique, their processors can generate several "harmony" parts simultaneously. Also referred to as "Diatonic Pitch Shifting".@Head@A hardware assembly, in close contact with the storage/playback medium used in magnetic or optical recording. A "Recording" or "Write" head induces physical changes in the surface of the medium, by which varying input voltages representing analog audio, video or digital data are recorded. The Playback, or Read head reconverts this information to its original form (voltage) during sound/video playback or data retrieval. For magnetic recording in particular, the Recording/Write head is essentially an electromagnet responding to an input voltage; its varying flux pattern is transmitted onto a magnetic coating on the moving tape or spinning disk. The Reproduce/Read head then registers these changing flux patterns as the media moves across it, reconverting them to output voltages.@Head Crash@Caused when the read/write heads of a hard disk make contact with the spinning surface of the disk. Due to the extremely small distances and rapid rotational speeds involved, head crashes can cause damage to the disk surface itself, the heads, and especially to your data on the disk. Avoid moving disks around while they are spinning (turned on), this includes the hard disk inside the chassis of your computer!@Headroom@The difference, in decibels, between the nominal operating level of an audio system and its maximum signal level before distortion. Useful for quantifying the difference between the average maximum level, used as a "zero" reference to avoid distortion caused by unexpected peaks in level, and another, higher level where clipping of the audio signal will actually occur.@Heal Separation@Digidesign Pro Tools command. Rejoins regions that have previously been separated with the Separate Region command, or other editing operations.@Helical Scan@Technology developed around 1960 for video recorders. The magnetic video tape wraps around a rotating drum, following a curving, helical path. The record/reproduce and erase heads are mounted on the rotating drum itself. In this manner, an entire video field is recorded in one pass, corresponding to a long helical strip at an angle across the tape's surface. The effective "tape speed" is a combination of both the actual tape transport's speed and the rotational velocity of the drum itself. DAT audio recorders (a.k.a. R-DAT) use similar technology to record PCM-encoded digital audio data on very small magnetic tape cassettes. Sometimes referred to as "Slant-Track Recording", Helical Scan tape recording accomodates very large amounts of information, without large tape widths or very high tape speeds, which make manufacturing more complicated and expensive. See DAT.
@Hertz, Hz@A unit of frequency, the number of times a cyclical waveform repeats per second (also known as cycles per second, or cps). Named for Heinrich Rudolph Hertz, a German physicist. Also abbreviated Hz. (One kilohertz, abbreviated kHz, is equal to 1000 Hz. One megahertz, abbreviated MHz, is equal to 1,000,000 Hz.)@Hex, Hexadecimal@Computing term. A numbering system based on 16 digits: 0-9, plus A-F. Hexadecimal numbers are "base 16", as opposed to the common "base 10" decimal system, or the "base 2" system of binary numbers. Commonly used in many computer and sampler operating systems. Sound editing programs such as Sound Designer often provide this method of numbering audio samples, to provide a common reference with certain other digital audio devices.@HFS@Hierarchical File System, the common disk directory structure used on the Apple Macintosh computer and Mac-compatibles, where files reside within folders (analogous to directories on a PC-compatible) which in turn can be nested within other folders. The user can use the mouse pointer to drag files and folders from one location to another on a disk. (Technical note: under the HFS structure, Macintosh files incorporate a data area known as a "resource fork", it indicates to the operating system whether the file is a program or document, from what program a document was originally created, its icon, etc. PC or ISO 9660 directory structures do not include this information.)@High Sierra@An early standard for CD-ROM data, based on the Yellow Book disk format. The High Sierra format was defined by a group of 12 manufacturers (the "High Sierra Group", including Apple, Microsoft, Sony and Philips) during a conference held at Lake Tahoe in 1985, to provide a single CD-ROM format that could be read by Macintosh, MS-DOS, Unix and VMS computers. The ISO 9660 CD-ROM format was based on a modified version of the High Sierra format. See CD-ROM, ISO 9660, Yellow Book.@Highpass Filter, HPF@A filter that passes through all signal components that are higher than a determined frequency, while attenuating frequencies below this Cutoff Frequency.@Hiss@An undesirable type of Broadband Noise, produced by analog tape and amplifiers.@HTML@HyperText Markup Language. A page-description and scripting language, used to format the appearance and interactive characteristics of "home pages" and related documents on a WorldWide Web (www) site being browsed over the Internet. Includes information about location and style of text and graphics, color, page dimensions, hypertext links to other documents and pages, sound, etc. within an interactive Web document. See also Internet, WWW, modem.@Hum@A steady low frequency signal, especially in the form of noise introduced into audio circuits, which is related to the 60 or 50 Hz frequency of the AC current supplying power to the device. Hum is often induced by improper shielding or grounding of audio components. If AC Hum (often called "sixty-cycle" hum in the U.S.) were a pure sine wave with no harmonics, it would be relatively easy to eliminate from an audio channel, through the use of a single notch filter. However, the AC hum waveform is often quite rich in harmonics, extending well into critical areas of the audio spectrum. For this reason, some Hum Removal algorithms (such as the one in DINR) utilize banks of harmonically related notch filters, with very narrow bands of rejection. See also Hiss, Broadband Noise.@Hybrid CD-ROM@A variant of the Yellow Book CD-ROM format, Mode 1, which permits a single CD-ROM disk to be used from either a Macintosh or PC-compatible computer. The simplest Hybrid CD-ROMs are multisession CD-ROMs, containing both an HFS volume (standard file structure for Macintosh disks), and an ISO 9660 volume (PC); these are also known as Multi-Volume hybrids. The data for each computer's operating system is separate; most Mac users will see both volumes on their desktop, while PC users see only the ISO 9660 volume. A "Shared Hybrid" CD-ROM also permits creating a single CD-ROM for both PCs and Macs. On shared hybrid CD-ROMs, a single disk volume contains separate directories for HFS and ISO files, plus other directories which can be shared by both operating systems, containing files compatible with both platforms (such as TIFF or PICT images, QuickTime movies, audio, etc.). This avoids duplication of large files, saving disk space. See also Yellow Book, CD-ROM.@HyperCard@Apple Macintosh software, written by Bill Atkinson and introduced in 1987. A multimedia assembly environment, permitting user to combine text, graphics, and sound, with interactivity provided by onscreen buttons, through the metaphor of "cards", "buttons", "fields", etc. The "cards" are contained in documents known as "stacks", modeled after a Rolodex-type indexed card file. Hypercard introduced the concept of hypertext to the general public (a non-linear approach to text authoring, with hot "links" between text objects by which the user navigates through the material), and is in fact still used for many tutorial and educational applications. Accepts XFCN and XMCD resources, for external control of sound cards, serial control; can also control CD-ROM drives for playback of audio CDs (see music exploration titles by Voyager and Warner New Media for excellent examples of this application of Hypercard).@Hyperprism@Software plug-in by Arboretum Systems. Realtime DSP and effects processing, including chorus, tremolo, flanging, filter effects, etc., on incoming signals from external or internal sources.@
