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Now looking at definitions starting with letter "i"

induction : A common means by which extraneous signals enter the audio path is through induction. All current produces a corresponding electromagnetic field that radiates from the conductor carrying the current. Conversely, a radiant electromagnetic field can induce current in a nearby conductor, introducing unwanted signals into an audio cable. Balanced lines are much less susceptible to induced noise because of the phase reversal in the wires. Two common sources of induced noise are RFI and EMI.

inductor : Used most often in crossovers and filters, an inductor is an electronic device whichwith presents a low impedance to DC (it allows it to pass), but an increasing impedance to AC as frequency rises. It has the opposite characteristic to a capacitor and is physically a coil of wire, sometimes with a ferrite core.

inertance : In acoustics, a sound barrier’s opposition to the flow of energy through it, a. Analogous to the inductance of an electronic circuit, and measured either broadband or split-band. Since a dense, highly reflective barrier exhibits high inertance, the term is not necessarily related to the absorption coefficient or sabine ratings of surface or insulating materials.

infinite baffle : A loudspeaker which is constructed in a totally sealed enclosure so that it completely separates the sound radiated from its back. The opposite of a ported enclosure.

infrasonic : Sounds or signals whose frequencies are below the normal human hearing range, about 20Hz, sometimes incorrectly called subsonic.

inharmonic : Containing frequencies that are not whole-number multiples of the fundamental. See harmonic, partial, clangorous.

initialization : The process of reading the table of contents from a CD after it has been inserted into a CD player. The player then displays the track numbers recorded on the disc. See Control and Display signals.

initialize : To reset a piece of equipment or program so as to revert to the parameter settings stored in its ROM, usually the factory presets.

input : (1) The connector by which a signal enters an electronic device. (2) The incoming signal, itself. (3) An electronic operating mode in tape recorders, in which the input signals to various tracks are routed directly to their outputs.

input level : The signal voltage or power present at the input of a device. See headroom headroom.

input stage : That portion of a mixer which consists of the microphone preamplifier.

insert editing : Used in videotape or digital audio editing to describe the process of replacing a segment located between two specific and previously dubbed segments. The editor usually refers to SMPTE timecode numbers.

insert point : Typically found on a mixer, but also on some other audio devices, a point at which a signal may be diverted through a breakjack. Inserting a plug breaks the bypassing connection and makes a new connection through the plug to the outside world. There may be two sockets involved with a normalled connection, one marked send and one marked return. On a mixing desk, the input might be connected to the send terminal of an insert point for sending the signal to a device such as a compressor, which then returns the modified signal back into the channel. If no such unit is plugged in, the signal bypasses the insert point. See channel insert, auxiliary send.

insertion loss : Signal level loss due to the addition of a passive audio device, such as crossover networks and equalizers, into a sound system, and measured in dBindB. There is also an insertion gain from amplifying circuits, but the term seems not to be widely used.

insulator : A material that is non-conductive, i.e., usually a material used to separate wires carrying electrical signals. Elements with few free electrons are the best thermal or electrical insulators.

integrated amplifier : A consumer audio component consisting of a preamp and power amp all in one chassis.

integration time : The time it takes for the human aural system to register and understand a sound. For example, human hearing more closely resembles a VU meter than a peak meter in that a very quickly peaking sound, such as a drum, may actually be very loud on an absolute scale, but is not perceived as loud as the decay is well in progress before the sound is fully processed, i.e., heard.

integrator module : A lowpass filter which increases the rise and fall times of a sound envelope, lengthening the attack and decay times. Compare with a differentiator module.

intensity : The strength of a signal or the brilliance of a video image.

intercut : The original magnetic recording editing technique whereby a section of magnetic tape from the master tape is physically cut out and replaced with another take using splicing tape.

interference microphone : See gun microphone.

interleaving : An error-concealment scheme in which data words or samples generated in sequence by the A/D converter are separated into defined subgroups such as odd- and even-numbered words within a longer sequence. Each subgroup is then recorded after its mate, shuffling originally adjacent words to positions somewhat far apart on tape. This is done to allow the reconstruction of continuous valid data in the event of large-scale drop-outs, burst errors, or other extended read error problems. Cross-interleaving further shuffles the interleaved data into yet smaller subgroups. The CIRC system, used in CD reproduction, combines several error-concealment algorithms, including cross-interleaving.

interlock : (1) A term that generically refers to two or more machines running in synchronization, often shortened to locked, or synched. (2) The projection of film footage and its corresponding sync sound, either the magnetic film transferred from the original sync tapes, or the completed final mix, in synchronization. (3) The system by which the projector and sound playback are synchronized during projection.

intermodulation distortion : While harmonic distortion adds frequencies that are harmonically related, intermodulation distortion adds nonharmonic partials to the original signal. IM is a measure of how two frequencies that are present at the same time affect each other. Amplitude intermodulation distortion is caused when combinations of two or more frequencies generate new frequencies which are sums and differences of the original signal, i.e., the amplitude modulation of one signal by another. If an amplifier is used to amplify each tone equally, but if the gain of the amplifier varies with signal level (i.e., it is nonlinear), high-frequency sounds will be amplified by different amounts depending on whether a nearby low-frequency sound is near zero or near its peak. Therefore, the high-frequency signal will undergo changes in amplitude at the rate of the low-frequency signal, modulating the high-frequency sound which will be heard to flutter in the presence of the low-frequency sound. PIM is another component of intermodulation distortion, but to a lesser degree.

international version : See M&E.

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