Energy Time Curve (ETC)

Simple Explanation

A graph that shows how sound energy fades over time in a room or system.

Concise Technical Definition

A time-domain graph showing the amplitude envelope (decay) of an acoustic signal, typically with energy in dB SPL on the vertical axis and time on the horizontal.

Layman-Friendly Analogy

Like a chart showing how loud a sound is right after a clap, and how quickly it fades away.

Industry Usage Summary

Used in room acoustics, loudspeaker testing, and tuning to visualize early reflections, direct sound arrival, and decay characteristics.

Engineering Shortcut

Plot of sound energy (in dB) over time; reveals reflections and decay profile.

Full Technical Explanation

The Energy Time Curve (ETC) is a graphical representation of how sound energy changes over time following a transient signal (such as a test sweep or impulse). Initially introduced as a 3D plot with time, energy, and frequency axes, it's now most commonly displayed in 2D with energy (typically in dB SPL) on the vertical axis and time on the horizontal. The ETC reveals key information about the direct sound, early reflections, and decay rate of a space or system. It is widely used in room analysis, system alignment, and acoustic treatment evaluation. Peaks on the curve can identify strong reflections or echo paths.

Related Terms

Acoustics, Amplitude, Decay, Direct Sound, Early Reflections, Frequency, Graph, Loudspeaker, Room, Signal, Sound