dB intensidade (I/I₀)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
This calculator converts sound intensity (I) into decibels (dB) using the formula 10·log(I/I₀), where I₀ is the standard reference intensity (10⁻¹² W/m²). It's used to determine sound pressure levels in acoustics, environmental studies, and engineering, where logarithmic scale measurements are critical for representing human hearing perception.
The formula calculates the ratio between measured sound intensity (I) and the reference intensity (I₀), applies a base-10 logarithm, and multiplies by 10. This transforms a linear quantity into a logarithmic scale that better reflects how humans perceive loudness. For example, a sound 10 times more intense than I₀ equals 10 dB.
Use this tool to assess noise risks in industrial environments, plan quiet zones in cities, or interpret technical sound equipment data. Precautions: ensure inputs are in W/m² and that measured intensity stays within the formula's valid range (avoid negative or null values).
Frequently asked questions
What is sound intensity level in decibels?
It's a logarithmic measure expressing the ratio between measured sound intensity (I) and a standard reference (I₀), enabling large auditory variations to be represented on a comprehensible scale.
Why does the formula use base-10 logarithm?
Logarithmic scale reflects how human ears perceive sounds: a linear increase in intensity (10x) is perceived as a linear increase in loudness (10 dB), not exponential.
What is I₀ in the formula?
The standard reference intensity is I₀ = 10⁻¹² W/m², corresponding to the human hearing threshold (0 dB).
When is this calculator not suitable?
It isn't valid for direct sound pressure measurements (pascals). Use it only when intensity is in W/m² and the sound source has isotropic conditions.