Potência Sonora
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
P = IA
About this calculator
The sound power calculator determines the acoustic power emitted by a sound source using the relation P = I · A, where P is power in watts, I is sound intensity in W/m², and A is the surface area in m². This tool is useful for audio engineers, sound technicians, and acoustics professionals, allowing them to calculate the total power radiated by a source from intensity measurements over a known area.
Operation is simple: enter the sound intensity (in W/m²) and the surface area (in m²). The calculation multiplies these values to obtain the sound power. For example, if a source emits an intensity of 0.01 W/m² through an area of 10 m², the power will be 0.1 W. This formula assumes uniform intensity over the area, which is an approximation for point sources or isotropic surfaces.
When to use? In practical situations such as sizing sound systems, environmental noise assessment, studio or concert hall design. It is also useful for calculating loudspeaker efficiency or comparing sound sources. Remember: sound intensity depends on distance; power is an intrinsic property of the source, independent of distance.
Cautions: The formula assumes all sound energy passes perpendicularly through the area. On curved surfaces or with reflections, power may be underestimated. Use consistent units (W/m² and m²). For directional sources, intensity varies; consider the average over the area. This tool does not replace precise laboratory measurements but offers a quick estimate.
Frequently asked questions
What is the difference between sound intensity and sound power?
Sound intensity is power per unit area (W/m²) and depends on distance from the source. Sound power is the total energy emitted per second (W) and is an intrinsic property, independent of distance.
Can I use this calculator for sound sources in air and water?
Yes, as long as intensity and area are measured under the same conditions. The formula is universal, but interpretation should consider the medium (different acoustic impedance).
What does surface area mean? How to measure it?
It is the area through which sound intensity is measured. For a point source, the area can be the surface of a sphere (4πr²). For planar sources, it is the area of the emitter itself.
Can this calculator be used for loudspeaker power?
Yes, but note that electrical power from the amplifier is not equal to sound power. Loudspeaker efficiency converts part of the electrical power into sound. This calculator gives the acoustic power emitted.
What if the intensity is not uniform over the area?
Use an average intensity value over the area. For accuracy, integrate intensity over the surface. The calculator assumes uniformity, providing an estimate.