glossary of terms for the audiophile |
 list of audio terminology
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Haas effect: If sounds arrive from several sources, the ears and brain will identify only the nearest. In other words, if our ears receive similar sounds coming from various sources, the brain will latch onto the sound that arrives first. If the time difference is up to 50 milliseconds, the early arrival sound can dominate the later arrival sound, even if the later arrival is as much as 10 dB louder. The discovery of this effect is attributed to Halmut Haas in 1949.
Harmonics: Also called overtones, these are vibrations at frequencies that are multiples of the fundamental. Harmonics extend without limit beyond the audible range. They are characterized as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic: second, fourth, sixth, etc.-is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand: third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasize odd-order harmonics tend to have a harsh, hard quality.
HDCD: High-Definition Compact Disc. A proprietary system by Pacific Microsonics that requires special encoding during the recording process. Some observers report HDCD discs as having better sound. To gain the benefits requires having special HDCD in your CD player.
Headroom: The ability of an amp to go beyond its rated power for short durations in order to reproduce musical peaks without distortion. This capability is often dependent on the power supply used in the design.
Head Unit: The in dash control center of a car audio system, usually consisting of an internal low powered amp, AM/FM receiver, and either a tape or CD player (or both).
Hearing Sensitivity: The human ear is less sensitive at low frequencies than in the midrange. Turn your volume knob down and notice how the bass seems to"disappear". To hear low bass requires an adequate SPL level. To hear 25Hz requires a much higher SPL level than to hear 250Hz. In the REAL world, low frequency sounds are reproduced by large objects; bass drums, string bass, concert grand pianos, etc. Listen to the exhaust rumble of a 454 cubic inch V8 engine vs. the whine of the little four banger. The growl of a lion vs. the meow of your favorite kitty. As frequency decreases we perceive more by feel than actual hearing and we lose our ability to hear exact pitch.
Hertz (Hz): A unit of measurement denoting frequency, originally measured as Cycles Per Second, (CPS): 20 Hz = 20 CPS. Kilohertz (kHz) are hertz measured in multiples of 1,000.
High-Pass Filter: A circuit that allows high frequencies to pass but rolls off the low frequencies. When adding a subwoofer it is often desirable to roll-off the low frequencies to the main amplifiers and speakers. This will allow the main speakers to play louder with less distortion. High-pass filters used at speaker level are usually not very effective unless properly designed for a specific main speaker (see impedance below).
Hiss: Audio noise that sounds like air escaping from a tire.
Home Theater: An audio system designed to reproduce the theater sound experience while viewing film at home. Minimally consisting of a Dolby Pro Logic® surround sound receiver, left and right front speakers, a center channel speaker, and two surround speakers. These plus optional subwoofer(s), surround speaker(s), and digital formats such as Dolby Digital® can enhance the viewing experience by drastically improving the sound quality of movie soundtracks.
Hum: Audio electronic noise that has a steady low frequency pitch.
Imaging: Listening term. A good stereo system can provide a stereo image that has width, depth and height. The best imaging systems will define a nearly holographic re-creation of the original sound.
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