dB SPL pressão
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The SPL pressure dB calculator converts sound pressure levels into decibels (dB) using the formula 20.log(p/p₀). It is crucial for measuring sound in contexts like audiology, acoustical engineering, and hearing tests. The reference pressure (p₀) is typically 20 micropascals (20 µPa), which corresponds to the human hearing threshold. The dB result indicates the relative sound intensity on a logarithmic scale.
To use the calculator, input the measured sound pressure (p) in pascals. The calculation compares this pressure to the reference value, amplifying the logarithmic scale to better represent human perception. For example, 100 dB SPL is ten times more intense than 90 dB SPL, even though the pressure difference is proportional. This makes comparisons easier in environments like concerts, industries, or home settings.
Remember that dB SPL measures effective pressure, not loudness. The formula assumes a sinusoidal sound wave and no distortions. In practical applications, use calibrated equipment to ensure accuracy, especially in medical or regulatory tests. Levels above 85 dB can cause hearing damage with prolonged exposure.
Frequently asked questions
Why does the formula use 20 instead of 10?
The factor 20 arises because sound pressure is a root quantity (amplitude), while sound intensity uses 10. The logarithmic scale correctly converts the relationship between pressure and intensity.
What is the standard reference pressure?
The standard reference is 20 micropascals (20 µPa), equivalent to the human hearing threshold at 1 kHz.
Can I use other reference values?
Yes, but it's crucial to keep the same reference value in all comparisons to ensure consistency in results.
What does a negative dB SPL value mean?
A negative value means the measured pressure is lower than the reference pressure. For example, -10 dB SPL indicates 10 dB below the hearing threshold.