Convert Sound Power Level (Lw) to Sound Pressure Level (Lp) instantly. Use our free Convert Sound Power Level to Sound Pressure Level calculator with formula & examples for accurate dB results.
Sound Power Level to Sound Pressure Level Converter
Convert sound power level (Lw) in decibels (dB) to sound pressure level (Lp) in decibels (dB).
Relationship Between Sound Power Level and Sound Pressure Level?
The sound power level (Lw) and sound pressure level (Lp) are both expressed in decibels (dB), but they measure different aspects of sound.
Sound power level represents the total acoustic energy emitted by a sound source, while sound pressure level measures the intensity of that sound as perceived at a specific location.
In simple terms:
Sound Power Level (Lw) is the sound produced,
Sound Pressure Level (Lp) is the sound heard.
Formula: How to Convert Sound Power Level (Lw) to Sound Pressure Level (Lp)
The standard formula used in this conversion is:
Lp = Lw + 10 · log10( Q / (4 · π · r²) )
Where:
- Lp = Sound Pressure Level (dB SPL)
- Lw = Sound Power Level (dB SWL)
- Q = Directivity factor (usually 1 for a free field)
- r = Distance from the source (meters)
You can use the Sound Power Level to Sound Pressure Level (Lw to Lp) calculator above to quickly perform this conversion.
Just enter:
- Sound Power Level (Lw) in dB
- Distance from the source (r) in meters
- Directivity Factor (Q)
Then click Calculate to instantly get the Sound Pressure Level (Lp) in decibels.
This tool is commonly used in:
- Acoustic engineering
- Noise control studies
- Environmental sound analysis
- HVAC and machinery design
- Audio system calibration
Understanding the Difference: SWL vs. SPL
- SWL – Sound Power Level (Lw)
- SPL – Sound Pressure Level (Lp)
Both use decibels (dB) but are measured differently:
- SWL (Lw): Total sound energy emitted by a source
- SPL (Lp): Measured sound pressure at a distance or point
For example, a fan may have a SWL of 85 dB, but the SPL you hear at 3 meters away may only be 70 dB, depending on environment and distance.
Convert Lw to Lp?
Converting from Sound Power Level to Sound Pressure Level helps you:
- Estimate how sound decreases over distance
- Predict noise levels for machinery or construction projects
- Compare acoustic performance of different devices
- Ensure compliance with environmental noise regulations
It’s especially useful for industries like manufacturing, HVAC, audio engineering, and environmental consulting.