belvolume

Belvolume is a coined term used in acoustics and signal processing to describe a logarithmic measure of the acoustic energy present within a specified three‑dimensional volume. It combines the bel, a historical logarithmic unit for sound intensity, with the concept of spatial volume to quantify how energy is distributed in space.

Definition: Let E_density be the average energy density (joules per cubic meter) inside a defined volume V, and let E0 be a reference energy density. The belvolume B is defined as B = log10(E_density / E0). Because the logarithm is base 10, B is expressed in bels; in many practical contexts it can be scaled to decibels by applying 10 × log10(E_density / E0).

Measurement and applications: Belvolume requires estimating the local energy density, typically from sensor arrays, simulations, or calibrated models of sound sources. It is used in room acoustics analysis, virtual reality and game audio to describe spatial loudness variations, and in noise-control planning where the energy distribution within a volume matters.

Status and interpretation: Belvolume is not an established SI unit or widely adopted standard. It appears in some theoretical discussions and speculative frameworks as a simple way to express spatial energy distribution on a logarithmic scale. As with any logarithmic spatial metric, its value depends on the chosen reference E0 and the defined volume V.

Examples: If E_density = 2 E0, then B = log10(2) ≈ 0.301 bels. If E_density = 0.1 E0, B ≈ −1 bel. See also bel, decibel, sound energy density, room acoustics.