What is the reference pressure used for SPL?

The standard reference sound pressure is 20 micropascals (20 µPa or 2×10⁻⁵ Pa), which corresponds to the threshold of human hearing at 1 kHz, as defined by ISO 1683.

What is the reference intensity for sound?

The reference sound intensity is 10⁻¹² W/m² (1 picowatt per square meter), which corresponds to the threshold of human hearing under free-field conditions.

Why does doubling the number of identical sources add only 3 dB?

Because the dB scale is logarithmic. Doubling the acoustic power (or number of identical incoherent sources) multiplies intensity by 2, and log₁₀(2) ≈ 0.301, so 10 × 0.301 ≈ 3 dB.

What is the typical SPL of normal conversation?

Normal conversation at 1 meter is approximately 60–65 dB SPL. A whisper is around 30 dB, a busy restaurant about 70–80 dB, and a jet engine at close range can exceed 140 dB.

What is the difference between dB SPL and dBA?

dB SPL is the flat (unweighted) sound pressure level. dBA applies an A-weighting filter that mimics the frequency sensitivity of the human ear, making it more relevant for assessing hearing risk and noise annoyance.

Can this tool handle very small or very large pressure values?

Yes. Enter any positive pressure value in Pascals. The tool will compute the correct dB result regardless of the scale, and will display a friendly error for zero or negative inputs.

Sound Pressure Level Calculator

Name: Sound Pressure Level Calculator
Availability: InStock
Author: Nham Vu

Calculate sound pressure level in dB from pressure values, or convert between SPL and sound intensity.

Calculation Mode

Pressure → dB SPL dB SPL → Intensity Combine Sources

Sound Pressure (Pa)

Reference: P₀ = 20 µPa = 2×10⁻&sup5; Pa

Enter values and click Calculate to see the result.

Copied!

Summary

Calculate sound pressure level in dB from pressure values, or convert between SPL and sound intensity.

How it works

Select a calculation mode: Pressure to dB, dB to Intensity, or Combine Sources.
Enter the required values in the input fields.
The result is computed instantly using the standard SPL formulas.
Review the formula and reference values shown below each result.
Use the copy button to copy the result to your clipboard.

Use cases

Verify SPL measurements from a sound level meter reading.
Determine sound intensity from a known dB SPL value.
Calculate the combined SPL when multiple identical speakers are running.
Assess workplace noise exposure against regulatory thresholds.
Academic physics and acoustics coursework problems.
Audio engineering and speaker placement calculations.
Environmental noise impact assessments.
Compare relative loudness between two sound pressure readings.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu