Glossary – H
Haas Effect – (Also called Precedence Effect) Simply stated, a factor in human hearing in which we perceive the source of a sound by its timing rather than its sound level. In his research, Helmut Haas determined that the first sound waves to reach our ears help our brains determine where the sound is coming from, rather than its reflection or reproduction from another source. The reflection of the sound must be at least 10dB louder than the original source, or delayed by more than 30ms (where we can perceive it as an echo), before it affects our perception of the direction of the sound. This is what helps us distinguish the original sound source without being confused by reflections and reverberations off of nearby surfaces. Understanding the Haas effect is particularly useful in live audio settings, especially in large venues where loudspeakers are time-delayed to match the initial sound waves coming from the source.
Half-Normalled – See “Normalled.”
Half Step – A change in pitch equivalent to adjacent keys on a piano. Also known as a “semitone.”
Hall Program –A setting of a digital delay/reverb effects unit that approximates concert halls. Hall programs are characterized by pre-delay of up to 25 ms.
Hard Knee – In compression, refers to a more abrupt introduction of compression of the signal once the sound level crosses the threshold. (See also “Knee.”)
Harmonic Distortion – The presence of harmonics in the output signal of a device which were not present in the input signal, usually for the purpose of changing the instrument’s timbre.
Harmonics – Whole number multiples of the fundamental frequency that occur naturally within the playing of a tone. Mathematically, if the fundamental frequency is x, the harmonics would be 2x, 3x, 4x, etc. For example, if the fundamental frequency of the note played is 440Hz (or A-440), the harmonics would be 880Hz, 1320Hz, 1760Hz, and so on. The presence of harmonics in the tone is what creates the timbre of an instrument or voice.
Head – In tape recording, an electromagnetic transducer that magnetically affects the tape passing over it. Recording/playback heads change the audio signal from electrical energy to magnetic energy and back, for recording and playback purposes. An erase head creates a powerful electromagnetic field to the tape to erase previous signals from the tape.
Headroom – The difference in dB between normal operating level and clipping level in an amplifier or audio device. Also describes the difference in dB between the peak levels of a recording and the point at which the signal distorts. (Also called “Margin.”)
Hertz (Abbreviated Hz)– 1) The unit of measurement for frequency, specifically, the number of complete wave cycles that occur in a second (cycles per second). 1 Hz = 1 complete wave per second. 2) A popular rental car company (not typically used in recording except for transport to the studio).
Hi-Hat – In drum sets, double cymbal on a stand, usually positioned next to the snare, which can be played with a foot pedal and/or by the top cymbal being hit with a stick.
Hi-Z – See “High Impedance,” “Impedance.”
High Impedance – (abbreviated Hi-Z) Described as an impedance or resistance of several thousand ohms. In microphones, Hi-Z is typically designated as 10,000 or more ohms. (See also “Impedance.”)
High-Pass Filter – An audio filter that attenuates signals below a certain frequency (the cut-off frequency) and passes signals with frequencies that are higher.
Highs or High-End – Short for “high frequencies,” loosely the frequencies above 4000 Hz. Usually meant in the context of “highs, mids and lows” in an audio signal.
Horn – 1) A speaker or speaker enclosure where sound waves are sent by a speaker cone or driver into a narrow opening which flares out to a larger opening. 2) One of several different types of brass musical instruments.
House Sync – A reference signal such as SMPTE time code that is used to keep all devices in the room in sync.
Hum – 1) The low-frequency pitch that occurs when power line current is accidently induced or fed into electronic equipment. The hum reflects the fundamental frequency of the current (60 Hz in the U.S., and 50 Hz in many European countries). 2) To vocalize a pitch without opening one’s mouth.
Hypercardioid – A variation of the cardioid microphone pick up sensitivity pattern in which the shape of the optimal pickup area is tighter and more directional than cardioid. Hypercardioid microphones are most sensitive directly on-axis in front of the microphone, and begins rejecting sounds between 90-150 degrees off-axis, depending on the tightness of the pattern.
Hz – An abbreviation for the term Hertz, or the unit of frequency.