Knowledge Centre · Understanding Noise
What is Sound Power Level?
Sound Power Level (SWL) can be thought of as the total amount of sound energy emitted by a noise source — one of the most fundamental measurements used in acoustics.
Read time
2 minutes
Relevant to
Anyone reading a noise report or condition
What Sound Power Level (SWL) stands for
SWL stands for: Sound Power Level.
Fortunately, it is much simpler than it sounds.
Sound Power Level (SWL) can be thought of as the total amount of sound energy emitted by a noise source, expressed in decibels (dB) — one of the most fundamental measurements used to describe how much noise a source generates.
A sound source, measured independently of distance
Every noise source produces a certain amount of sound energy. Unlike Sound Pressure Level (SPL), which changes depending on where the measurement is taken, Sound Power Level (SWL) is a property of the source itself.
This means the Sound Power Level of a generator, fan or piece of machinery remains the same whether it is measured close to the source or further away. Because of this, SWL is widely used to compare the noise emissions of different products and equipment.
Engineers can then use the Sound Power Level to predict the Sound Pressure Level at different distances and locations.
If a generator has a Sound Power Level of 105 dB, it means the generator emits a total sound power of 105 decibels, regardless of where a listener is standing. The actual Sound Pressure Level experienced by a person will depend on factors such as distance, surrounding buildings, barriers and ground conditions.
Where is Sound Power Level (SWL) used
Sound Power Level is commonly used to describe the noise emitted by equipment and machinery.
Typical applications include:
- Product and equipment testing – determining the sound power emitted by machinery, appliances and industrial equipment.
- Environmental noise modelling – predicting noise levels at nearby receivers using source sound power data.
- Building services – assessing HVAC systems, cooling towers and mechanical plant.
- Equipment specification and procurement – comparing the noise performance of different products before purchase.
- Research and acoustic investigations – providing standardised source data for acoustic analysis.
Related reading
Try the calculator
See how multiple sound levels combine logarithmically, not by ordinary addition.
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