Acoustic power (P)

Professional Definition

Acoustic power is the total amount of acoustic energy radiated by a sound source in a unit of time through a closed surface surrounding that source. It is a physical quantity that characterizes the source itself, independent of the environment in which it is located or the distance of the measuring point.

This quantity is denoted by the symbol P, and its unit in the SI system is Watt [W]. In engineering practice, due to the vast range of acoustic energy values found in nature, it is more common to operate with the logarithmic acoustic power level (denoted as LWA), expressed in decibels. This is an input parameter essential for creating acoustic maps and modeling noise propagation in the environment.

Acoustics in Simple Terms

To understand the difference between power and acoustic pressure (i.e., what we hear), it is best to use the analogy of an electric heater or a light bulb. Imagine a heater with a power of 2000 W. This value is its inherent characteristic – regardless of whether you place it in a small bedroom or a large warehouse, it will always generate 2000 W of heat. This is the acoustic power of the source.

However, how warm it feels to you (i.e., the temperature at a specific point in the room) depends on how far you are from the heater, whether the room is insulated, and how large it is. This is analogous to acoustic pressure – what we actually perceive with our ears. Therefore, acoustic power tells us about the