soundfield

A soundfield is the spatial distribution of sound in a region of space, described by acoustic pressure and particle velocity as functions of position and time. In air, sound is characterized by the acoustic pressure p(x,t) and the particle velocity vector v(x,t). The pair determines the energy density and the direction of energy flow, which can be summarized by the acoustic intensity I, typically considered as a time-averaged product of pressure and velocity.

In an free field away from boundaries, the soundfield is governed by the wave equation and can be represented as a superposition of waves, such as plane waves. Near boundaries and in enclosed spaces, reflections create more complex patterns, including direct sound, early reflections, and reverberation. For harmonic analysis, fields are often analyzed at a single frequency using complex amplitudes to describe phase relationships between pressure and velocity.

Measurement and analysis of soundfields rely on pressure sensors and arrays to map p(x,t) and, in some techniques, velocity or pressure-velocity combinations. Ambisonics and specialized soundfield microphones aim to capture the full spatial information of the field. Reconstruction methods such as beamforming and near-field acoustical holography interpret or reproduce the field, while soundfield synthesis uses loudspeaker arrays to recreate a desired field in space.

Applications span architectural and room acoustics, loudspeaker design and placement, noise control, and audio recording for VR and AR. The term emphasizes the complete spatial character of sound, beyond simple loudness, including its directionality, phase, and energy flow.