Simple Explanation

A 3D graph that shows how sound energy fades over time across different frequencies.

Concise Technical Definition

A waterfall display or 3D plot showing the amplitude of frequencies over time, used to analyze how quickly or slowly different frequencies decay in an audio system.

Layman-Friendly Analogy

Like watching ripples in a pond after you drop a stone—some fade quickly, others linger. This shows how long sound "echoes" at each frequency.

Industry Usage Summary

Cumulative spectral decay (CSD) plots are used in speaker design, room acoustics, and measurement software to visualize the decay characteristics of a system after an impulse. They help engineers identify resonances, room modes, and lingering energy at specific frequencies. CSD plots are commonly used in loudspeaker testing, microphone calibration, and evaluating room treatment effectiveness.

Engineering Shortcut

CSD = Frequency vs Amplitude vs Time (aka Waterfall Plot). Long decay = possible resonance.

Full Technical Explanation

Cumulative spectral decay (also called a waterfall display) is a three-axis graph used in acoustic analysis. It maps frequency (horizontal), amplitude (vertical), and time (depth) to show how sound energy at various frequencies diminishes after a signal stops. This tool reveals how quickly a loudspeaker, room, or system can dampen energy. Peaks that persist indicate resonant behavior, while sharp drops show fast decay. Engineers use this to refine driver designs, crossover filters, and acoustic treatments.