The acoustic quantity sound power refers to the sound energy emitted by a sound source per unit of time. Its unit is watt (W). The associated logarithmic quantity is the sound power level. The sound power is used to clearly identify a source.
The sound power is independent of the environment in which a sound source is operated. That is why the EU Directive 2000/14/EC is based on sound power. Products imported into the EU must sometimes have a so-called ‘noise label’. This sticker informs the consumer or user about the sound power, making it easier to compare different products. Sound power is also very important when planning industrial plants.
The sound power can be determined either by measuring the sound pressure level on an envelope around the object (ISO 3740 to 546) or by measuring the sound intensity (ISO 9614).