Sound pressure level calculator
Convert between sound pressure (Pa) and sound pressure level (dB SPL), and compare values at 2 distances side by side. The reference sound pressure is 20µPa, and the calculation assumes a point source in a free field without reflection or absorption.
What you can do
Convert between Pa and dB SPL
Enter a known sound pressure or sound pressure level to view the same condition in Pa and dB SPL.
Compare different distances
Enter the original distance and a comparison distance to view sound pressure and sound pressure level side by side using the point-source model.
How to use
Enter sound pressure or sound pressure level
Choose Pa or dB SPL as the input unit, and enter the known value at the original distance.
Specify the original and comparison distances
Enter the original distance from the sound source and the distance to compare, in m.
Check the original and comparison values
Press “Calculate.” Compare the same items on the left and right, and copy or save all 4 results together if needed.
Useful when
Learn the relationship between sound pressure and level
Check how many dB SPL a sound pressure expressed in Pa represents relative to the reference sound pressure of 20µPa.
Calculate changes with distance
Compare how the modeled sound pressure level changes when moving farther from or closer to a point source.
Reference sound pressure and distance model
0dB SPL does not mean silence
The reference sound pressure for this calculation is 20µPa. 0dB SPL is sound pressure equal to that reference; it does not mean the sound pressure is 0.
Point-source, free-field model
Calculated assuming sound pressure is inversely proportional to distance. Doubling the distance reduces the level by approximately 6dB. Room reflections, obstacles, and absorption are not included.
Distinguish it from dB values in audio files
dB SPL is a ratio relative to a reference sound pressure. It cannot be treated as the same value as digital audio dBFS or frequency-weighted dB(A).
Frequently asked questions
Can distance alone accurately determine sound levels in a room?
This calculation uses a point-source, free-field model. It does not account for reflections, the spatial extent of the source, or obstacles, so it does not accurately predict actual sound in a room.
Is there a microphone-based sound measurement feature?
This screen converts the numbers you enter. It does not measure sound pressure using a microphone or determine whether noise meets a standard.
Can I enter negative dB SPL values?
Yes. Sound pressure below the reference produces a negative dB SPL value. When entering Pa, specify a value greater than 0.
Input and results
- Input
- A value in dB SPL or Pa, and the original and comparison distances.
- Results
- Sound pressure level and sound pressure at the original and comparison distances.
- Save
- Copy all 4 items together or save them as TXT. Changing the input clears the previous results.