Simple Explanation

A type of distortion where mixed sounds create extra, unwanted tones that weren’t in the original audio.

Concise Technical Definition

A form of distortion caused by nonlinearities in a system, where two or more input frequencies interact and produce additional frequencies that are not harmonically related to the originals.

Layman-Friendly Analogy

Like playing two notes on a piano and hearing weird extra notes that don't belong—those extra notes are intermodulation distortion.

Industry Usage Summary

Measured in amplifiers, loudspeakers, and processors to assess nonlinear performance; more disruptive than harmonic distortion because it creates unrelated, harsh-sounding artifacts.

Engineering Shortcut

Non-harmonic sum/difference tones = IMD; from nonlinear system behavior.

Full Technical Explanation

Intermodulation Distortion (IMD) arises when a nonlinear audio component (e.g., amplifier, loudspeaker) processes multiple frequencies at once, causing them to interact and produce sum and difference frequencies that are not harmonically related to the original signals. For example, if a system receives two input tones at f₁ and f₂, it can generate distortion components at f₁ ± f₂, f₁ ± 2f₂, 2f₁ ± f₂, etc. These intermodulation products can sound harsh or unnatural, especially in music with complex harmonics. IMD is particularly problematic in loudspeakers, where physical limitations of the diaphragm contribute to these nonlinearities. It is often tested using two-tone or multitone signals to simulate real-world audio content. Lower IMD indicates cleaner, more accurate audio reproduction.