Audio Terminology And Definitions Dictionary
I2R: Formula for power in watts, where i=current in amperes,
R=resistance in Ohms.
IF Intermediate Frequency to which RF signals are
converted in a radio tuner.
attribute (usually of a pair of speakers) that describes how well a projected
sound emulates a live performance by real instruments in a spatially convincing
manner (i.e., with a sense of width, depth, and "air" that accompanies a
live performance). If a system conveys an accurate image, the listener is often
able to place specific instruments in a specific position.
The resistance of a component or complete circuit to the flow of electrons.
Impedance is usually expressed in Ohms (represented by the Ohm symbol).
Impedance plays a role anytime a signal transitions from one circuit to another
or from one component to another. Impedance is rarely constant. Instead it
varies as the frequency of the signal changes. That's why impedance
measurements are rarely applicable in the real world. Impedance is particularly
relevant when discussing the signal transition from amplifier to speaker.
So-called "low impedance" speakers (those with nominal ratings of four ohms
or less) tax an amplifier's ability to reliably deliver sufficient current to
control driver movement.
Inductance A measure of reactance with comparable
but different audio effects to capacitance. The measuring
unit of inductance is the Henry.
Inductor Solid-state component with a particular Henry value.
A speaker enclosure that isolates the waves produced by the driver's front
surface from the "backwaves" produced by the driver's rear surface.
Infinite baffle enclosures are similar to acoustic suspension enclosures except
for the fact that they are usually much larger than their acoustic suspension
Insertion Loss A
drop in signal level caused by the addition of a component to the audio signal
This refers to when a video image is displayed on a screen by scanning each of
the two fields that make up a complete video frame. With interlaced scanning,
the odd-numbered lines (1, 3, 5, 7, etc.) that together make up the first field
are scanned across the display first. They are followed immediately by the
second field, which is composed of the even-numbered lines (2, 4, 6, 8, etc.).
Our eye-brain visual system does not fully process these fields quickly enough
to make us aware of the fact that they have been scanned individually. Rather,
it combines them into a series of single frames, each displayed every
one-thirtieth of a second.
(IM) A form of distortion where unwanted artifacts appear at frequencies that
are sums and differences of the input signal. For example, a signal composed of
both 400 Hz and 2000 Hz tones may contain spurious tones of 2400 Hz (the sum of
the original tones) and 1600 Hz (the difference between the original tones).
Intermodulation distortion is far more audible, and thus more objectionable,
than harmonic distortion.