Haas effect : The Haas Effect refers to the brain’s ability to integrate incident sound and early reflections into a single sound. Those early arrivals which occur within the first 5-35ms that are not more than about 10dB louder than the direct sound will be combined and added to the first arrival and localized to its source. If the delayed sound is more than 10dB louder or the delay is greater than 35ms, the listener will perceive distinct echoes.A psychoacoustic phenomenon where an instrument or sound’s apparent localization will shift in the direction of the earliest signal. This is a type of sensory inhibition which causes the response to the direct sound source to inhibit response to the reflections. Haas further noted
the Precedence Effect: the position of a perceived sonic image created by two sound sources depends on both the arrival times and the relative levels. If two sound sources arrive at the same time and at the same level, human aural perception will image the sound toward the centerpoint between the two sounds. If two sounds are equally loud, the image will shift toward the earliest-arriving signal. Further, if one source is louder, the image can be moved back to the center between the two sources by adding delay, provided that the delay time is less than 25ms. Beyond 25-30ms, the ear begins to hear the delayed sound as a discrete echo and the image shift effect no longer works. This phenomenon is usually used to simulate a stereo image in a monophonic recording where the original signal is panned hard left and a copy is delayed (1-50ms delay) and panned hard right. The Precedence Haas Eeffect may be mitigated by slightly attenuating the volume of the dry sound.
half track : (1) A recording format in which two parallel tracks are recorded in a single pass on a tape, each track using slightly less than half of the tape width. On some machines, a very narrow track with SMPTE or other synchronizing information is recorded and reproduced in the guard band. In this case, the data is frequency-modulated onto a very high-frequency tone in order to minimize crosstalk or bleeding into the audio. (2) A tape machine which records on half of the tape width only. This allows the tape to be inverted at the end of its play time, doubling the recording time for a given
length of tape. See also two-track, four-track."
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half-space loading : The placement of a loudspeaker against a wall or other hard, reflective surface. Such a placement typically improves the performance of a loudspeaker, enabling a wider dynamic range, as well as improving the amplitude response of the speaker. An alternative to placing the loudspeaker in a free-field.
half-step : The musical interval of a minor second in a diatonic scale, equal to 100 cents. In equal temperament, there are twelve semitones in each octave, so in the equal tempered scale, the minor second has a frequency ratio of the , or about 6%. In just intonation, the minor second has a frequency ratio of 15/16 . Also called a semitone. See scale.
half-time : See alla breve.
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handles : Sound sections between works in a production track that enable the re-recording mixer to cross-fade smoothly between shots with different backgrounds and/or room tones.
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handshaking : In data transmission, the process of checking that a receiving device is ready to receive, or that a transmitting device is ready to transmit. Also, the method whereby such checking takes place. In MIDI, handshaking occurs in System-Exclusive, where messages are sent between two devices to ensure that both are present and that both have received or transmitted blocks of data.
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hang : In film, the act of playing back a given element during a mix for the purposes of adding the track(s) to the mix. "We won’t premix the Foley cloth but will hang it at the final mix instead."
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hangover : The resonance which continues in a loudspeaker cone after the input signal has stopped. See also damping factor, impulse response, ringing.
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hard disk recording : A computer-based form of tapeless recording in which incoming audio is converted into digital data and stored on a hard disk. The digital counterpart to direct-to-disc analog (vinyl) recording, but being digital, the recording can be edited.
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hard knee compression : A characteristic of certain designs of a compressor wherein nothing happens to an input signal until the signal reaches the threshold limit, but as soon as it does, the full level of gain reduction is applied, as determined by the ratio control setting. A graph of the input gain against the output gain will show a sharp change in slope at the threshold level. Compare with soft knee compression."
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Hardware : Any tangible physical computing asset.
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harmonic : A frequency that is a whole-number multiple of the fundamental. For example, if the fundamental frequency of the sound is 440Hz, then the first two harmonics are 880Hz and 1.32kHz. A harmonic is the same as a partial where the partials exhibit the property that the overtones are mathematical multiples of the fundamental frequency. See harmonic series, Appendix C.
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harmonic distortion : The onset of harmonic distortion is the displacement of energy from a single frequency to its harmonics. The presence of harmonic frequencies added to an output signal by an electrical circuit or speaker, generally undesirable, caused by the system not being perfectly linear, such as when an amplifier is operated in a nonlinear portion of its transfer curve.
It is expressed as a percentage of the original signal:
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(Total Signal - Fundamental Signal) THD = Total Signal In a perfect audio device, such as an amplifier or tape recorder, the output signal would be a replica of the input signal with no changes except possibly the amplitude of the signalmaybe power level. See also doubling.
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harmonic enhancement : A technique used by aural enhancers. See harmonic synthesis."
harmonic envelope : The natural decay in the harmonics of a natural instrument over time.
harmonic series : A set of all of the frequencies which are an integral multiple of the frequency of the lowest tone, or fundamental. Humans perceive a harmonic series as a single pitch whose tonal quality is determined by the exact mix of related harmonics present. Below are illustrated the first sixteen harmonics in the harmonic series for the fundamental, C=65.4Hz. The notes indicating the 7th, 13th, 14th and 15th harmonics occur slightly flat or sharp of the notated pitch.See harmonic, partial.
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harmonic series tuning : A tuning system which is based on the first sixty harmonics of the tonic, resulting in a tuning which is not based on the usual diatonic scale. There are more notes per octave as the tuning progresses up the harmonic series; the top 32 keys of a keyboard cover one octave in pitch.
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harmonic structure : The sequence of chords used in a piece of music.
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harmonic synthesis : A technique used by aural enhancers which creates new high-frequency harmonics not present in the original recording. Adding a small amount of carefully controlled distortion can make a sound quality appear cleaner and more detailed. This happens by sending some dry sound to a side-chain highpass filter. The output of the filter is processed dynamically to add phase-shift and create synthesized HF (only) harmonics related to the dry signal.
harmonizer : See pitch-shifter.
hat : See top hat.
haystack filter : See bell filter.
HBA : host bus adapter. Hardware that provides interface services, both at the PHY and logical layers, between some communication standard and a computer’s operation system.
HCA : Host Channel Adapter. The IB component that connects a processor to other IB devices. An HCA is a bridge and must communicate with both other HCAs and TCAs. HCAs hookup, somehow, to your PC. Just how isn’t yet established, though they may be integrated onto the motherboard, presenting and external physical connector for linking, it should allow I/O subsystems, like Ethernet, fibre Channel, SCSI and interprocessor communication to converse through the infiniBand switch fabric, without complex hardware or software interfaces.
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HDCD : High Definition-Compatible CD. A trademark dithering process by Pacific Microsonics. The "HDCD process effectively cancels the additive distortions and simultaneously provides additional data to reduce the subtractive distortions" and is compatible with existing consumer digital playback equipment, claiming that there is a clear improvement in the fidelity of the conventional CD. The process works by converting an analog signal into a digital signal with a word length of "longer than 16 bits" and at a sampling frequency of "greater than 100kHz." These data can then be encoded into the standard CD format, or used with 20- or 24-bit recording/editing hardware/software. When used with an
HDCD decoder, the reconstructed signal is output at the appropriate > 16-bit, > 44.1kHz format."
HDTV : High Definition TeleVision. A term designating any television system using many more than the standard number of lines per frame specified in the NTSC, PAL, or SECAM systems. Experimental HDTV systems have been developed to provide high-resolution computer animation for motion pictures, flight simulators, etc., but are unlikely to be used for broadcast any time soon due to their inherent incompatibility with existing broadcast standards. The HDTV standard includes 5.1 audio, using AC-3">AC-3 encoding."
head : (1) On a tape recorder, an electro-magnetic transducer that (i) converts electrical energy in the signal into a magnetic field that induces magnetization in the tape, or (ii) produces an electrical signal in response to the varying remanent magnetism stored along a passing length of tape. See erase head, playback head, record head, sync head. (2) In general, the transducing mechanism used in recording or playing back signals on various media, e.g., the cutting head of a record mastering lathe, the optical head of a motion picture projector, etc.
head gap : See gap.
head losses : Limitations in the frequency response of the signal a tape head can transfer to or read from tape due to its inherent design or construction.
head shield : A metal shield installed around as much of the playback head as is possible, in order to minimize distortion due tokeeping EMI from being picked up.
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head stack : The assembly of tape heads in a magnetic recorder. The head stack normally consists of an erase head, a record head, and a playback head. Also called a head block.
Header essentially metadata that describes what is contained in the essence, packet, frame, or file remainder that follows, Typically, it is the part of a packet or frame that indicated the start of the data essence or payload; also, a preamble. Headers usually contain metadata such as addressing and error detection information.
headphone box : See cue box.
headphone mix : See cue mix.
headroom : The amount of additional signal above the nominal input level that can be sent into a module before clipping distortion occurs. On a digital tape, input levels are set very low, -15VU to -12VU, to allow adequate headroom for occasional input peaks that might exceed -12VU. See dynamic headroom, dynamic range, overs.
heads-out heads out: A tape recording which has been rewound and is ready to play. It is generally considered best for long-term storage to leave recordings tails-outtails out for minimum print-through.
helical scan : A type of videotape, data, or audio recorder in which the tape is wrapped around a large rotating drum, on which the actual record and playback heads are mounted. Since the heads rotate quickly and write parallel tracks at a very small angle with respect to the tape path, the signal written on the tape is may times the actual length of the tape itself. Thus, helical scan recording offers very high resolution at low tape speeds. Almost all consumer and professional videotape formats employ the helical scan principle, largely replacing the quadruplex recorder.
Helmholz resonator : A structure used in loudspeaker systems which is designed to resonate at a particular frequency. Because of the particular design of the resonator, the sound at the tuned frequency is dampened, and two bands, one each of higher and lower frequency, are produced, extending the bass response of the loudspeaker.
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Henry : (1) See Jecklin disk. (2) A measurement for inductance.
Hertz (Hz) unit of measurement for frequency, often written as Hz, or kHz (kilohertz).
heterodyne : To mix two frequencies together producing the sum and difference of the two input frequencies; any information contained on either original frequency is continued in the sum and difference frequencies. Heterodynes are used as the basic designmodel for all AM, FM, amateur radio, CB, TV, radar, and satellite systems. See amplitude modulation.
HFS : Hierarchical File System. A Mac-specific logical file format for CDs. CDs written in HFS cannot be read on PCs. Compare with ISO 9660.
hi-fi video sound : The result of encoding the stereo soundtracks input to hi-fi type VHS or Beta format videotape recorders on an frequency modulated carrier wave. This information is recorded along with picture data via the video record heads. Reproduction of hi-fi sound approaches digital quality audio.
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high band : A type of video system in which the picture information is encoded on a much higher carrier frequency than early color video systems; the broadcast standard currently in use.
high-fidelity : Refers to the reproduction of sound with little or no distortion. At least 15kHz of audio bandwidth is required for stereo high-fidelity.
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high-frequency compression : See HX/HX pro.
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high-output low-noise (HOLN) : A type of magnetic recording tape with very high sensitivity to applied magnetic fields, and with a very high S/N ratio, commonly used in professional audio applications.
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highpass filter : A filter that attenuates the frequencies below its rolloff frequency.
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HiPPI : High-Performance Parallel Interface): As the guys a CERN say, “it’s not just for supercomputers anymore.” Also known as GSN, or Gigabyte System network, HiPPI is one of the original high-speed LAN technologies and interoperates with Ethernet, fibre channel and ATM. It is an ANSI standard for a full-duplex, low-latency, point-to-point interconnect providing 100 to 200 Mbytes/second over a 50 twisted-pair copper PHY with a maximum length of 25 meters. A serial
version uses a glass-fiber PHY at the same speed; future versions will scale up to 6.4 Gbits/second.
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hiss : Audio noise that sounds like air escaping from a small aperture. See Barkhausen effect.
hit point : See cue.
hold time : An envelope parameter that specifies how long the attack segment of an envelope is to be held at full level.
hole-in-the-middle effect: An undesirable effect due to an extreme angle used with a coincident pair where the stereo image is all left and right, with very little sound in the center. Or, a similar phenomenon created by a surround system where the loudspeakers are too far apart to deliver balanced sound adequately to all seats in a theater.
hook : In popular music, the short melodic idea designed to be instantly memorable. It is often used for the chorus of a song, as well as for a fade.
horn : A type of loudspeaker enclosure named for its characteristic shape, with the speaker itself mounted in the narrow end of its tapered interior surface. Because the sound waves emanating from the speaker itself are internally enlarged before they exit from the larger end of the tapered surface, horn enclosures are highly efficient. Also, any horn-shaped device placed in front of a speaker to disperse sound.
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horn tweeter : A high-frequency loudspeaker which has a horn-shaped flare fixed to the front in order to increase acoustic efficiency and better control the directivity.
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hose : Slang term for an audio cable, e.g., a microphone cable or a snake.
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Host : A host can be thought of as a server. By the time IB is implemented, servers will mostly be IU rackmounted boxes rather than the floor-standing tower configuration that are now common.
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Host, to Host : Host, to host can be thought of as a sever, though, strictly speaking, a host can be any computer connected to a network. Servers range from single-chip microcontroller to 1U rack mounted boxes on up to a refrigerator-sized “big iron” that can simultaneously process millions of complex financial transactions per second.
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hot : In a balanced line system, the conductor which carries the in-phase component of a signal. For example, pin 2 of an XLR connector.
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hot hole : In film, slang for the projector gate itself, where the picture start mark is threaded up at the beginning of a session.
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Hotspot : nodes of APs that provide 802.11a/b/g services.
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house mix : An output on a sound reinforcement control console that is used to feed the power amplifiers for the loudspeakers in the venue, usually highly equalized to correct for house modes.
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house mode : The unique acoustic profile of a particular performance or recording venue. It is necessary to know the reverberation patterns within the space so that microphones, speakers, acoustic damping, etc. can be appropriately placed to produce or simulate the spatial and ambience effects desired, or to correct for room modes.
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house sync : An internal master timing reference used to synchronize all tra nsports within a facility.Also called black-burst.
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HPF : See highpass filter.
HRIR : Head-Related Impulse Response. See HRTF.
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HRTF : Head-Related Transfer Function. A function used to find the sound pressure that an audio source produces at the ear-drum. This is described by the impulse response from the source to the ear drum, called the Head-Related Impulse Response (HRIR), and its Fourier transform is the HRTF. The HRTF captures all of the physical cues to the source localization; once the HRTF for the left and right ears is known, accurate binaural signals may be synthesized from a monaural source.
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HSS : HyperSonic Sound.™ A loudspeaker technology developed by American Technology Corporation. This design produces audio by mixing an ultrasonic carrier with audio sidebands, in much the same manner of heterodyning. The mixing takes place in the air, relying on the nonlinearity of the atmosphere. The resultant sound is actually not generated at the transducer, but all along a projected column of ultrasonically vibrated air in front of the transducer as a conversion by-product of the interaction of the ultrasonic waves. Inaudible ultrasound energy is projected, which in turn emerges as AF sound from adjacent reflective surfaces. An acoustical sound wave is created in the air molecules by down-converting ultrasonic energy into the AF. This process supposedly is free of the problems of conventional speaker voice coils, cones, crossover networks, or enclosures. In addition, because sound is generated along the entire length of the projected column, there is minimal (1dB) amplitude loss as a function of distance from the transducer, across an average-sized room.
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hub : The cylindrical plastic or metal center of a tape reel to which the tape is attached and around which it is wound.
hum : Audio noise that has a steady low-frequency pitch, typically caused by the effects of induction of nearby AC lines or leakage of AC line frequency into an amplifier’s signal circuits, usually at 60Hz or 120Hz.
hum switch : A switch found on some audio equipment, such as amplifiers for musical instruments, which reverses the neutral and hot leads of the power cord in order to reduce hum. The ground lead is unaffected.
humanize : To introduce slight, random variations to the timing, velocity, duration and possibly other parameters of a track to make quantized tracks sound more natural. See percentage quantization.
HX/HX Pro : Headroom eXtension. A special circuit developed by Dolby Labs to reduce the tendency in cassette recorders toward self-erasure. In magnetic tape recording, loud, high frequencies in the signal look like bias to the tape which will tend to erase the signal as it is being recorded. The effect is called high frequency compression. The HX Pro system senses the level of high frequencies and reduces the level of bias dynamically.
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hyper threading : allows the CPU to act more like dual processors that can run two applications simultaneously, or run a single application significantly faster than on a standard processor.
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hypercardioid microphone : The narrowest of the unidirectional patterns, the hypercardioid is a variation on the cardioid microphone pick-up pattern which is most sensitive at the front and sides, while rejecting sounds entering 110°-250Ëš to the rear, with a small lobe of sensitivity at 180Ëš to the rear. The pick-up pattern of a hypercardioid is narrower than that of a supercardioid , and is somewhat similar to that of a figure-eight mic, but the response is asymmetrical in that the hypercardioid has greater sensitivity to sound arriving at the front of the capsule than to sound arriving a the rear. See acceptance angle. Also called a cottage loaf mic in the UK, for reasons related to bread.
hyperinstrument : An instrument which has had its sound-producing capability enhanced electronically.
hysteresis : In magnetic tape recording, the hysteresis inherent in the process of magnetizing the tape represents a large nonlinearity, and this causes harmonic distortion. The use of bias in the recording process reduces the effect of the hysteresis, and hence, reduces the distortion. Compare with Barkhausen effect.
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hysteresis loop : The graph of applied magnetic force vs. remanent magnetism. One measure of a specific recording tape’s performance.
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