I

IASCA (International Auto Sound Challenge Association)
Sound quality competition organization. Judges score imaging (30 pts), tonal accuracy (25), noise (20), dynamics (15), installation (10). Total: 100 points. → See also: SQ, dB Drag
Chapter 13.2

IIR (Infinite Impulse Response)
Digital filter using both input and feedback (output fed back). Computationally efficient. Used in parametric EQ and most crossovers. Causes phase shift. → See also: Biquad, FIR
Chapter 12.3

Imaging
Perceived location of sound sources in stereo field. Good imaging: vocalist centered at dashboard, instruments spread left-right. Requires: matched speakers, time alignment, proper tweeter placement. Worth 30 points in IASCA SQ judging. → See also: Soundstage, Time Alignment
Chapter 13.2

Impedance (Z)
AC resistance measured in ohms (Ω). Speaker nominal impedance: 2, 4, or 8Ω typical. Amplifier must be stable at speaker impedance. Lower impedance = more current = more power (if amplifier can deliver). → See also: Ohm's Law
Chapter 1.3

Impulse Response
System's output to very short input pulse. Shows time-domain behavior. Reveals: driver arrival times (for time alignment), room reflections, resonances. Measured with REW. → See also: REW, Waterfall
Chapter 4.3