Sound Intensity Calculator
Calculate sound intensity, sound power, distance from a sound source, or sound intensity level in decibels using standard acoustic formulas.
Acoustic Intensity Calculator
Select a calculation type and enter the available values.
Calculation Result
Find intensity, power, distance, or decibel level.
Convert common power, distance, and intensity units.
Calculations are completed directly in your browser.
How to Use the Sound Intensity Calculator
Calculate acoustic values without manually rearranging complicated equations.
Select a calculation
Choose whether you want to calculate intensity, power, distance, or sound level.
Enter known values
Add the available measurements and select their corresponding units.
View your result
Press the calculate button to receive the converted result and scientific notation.
What Is Sound Intensity?
Sound intensity describes the amount of sound power passing through a unit area. It indicates how much acoustic energy travels through one square metre in a particular direction. The standard unit of sound intensity is watts per square metre, written as W/m².
For a point source radiating sound equally in every direction, the sound spreads over the surface of an expanding sphere. As distance increases, the same sound power is distributed over a larger area.
In this formula:
- I is sound intensity in W/m².
- P is sound power in watts.
- r is distance from the source in metres.
- π is approximately 3.14159.
Inverse-Square Relationship
Sound intensity follows the inverse-square law in a free field. When the distance from a point source doubles, the sound intensity becomes one-quarter of its previous value. When the distance triples, the intensity becomes one-ninth.
Sound Intensity Level in Decibels
Because sound intensity values can vary across an extremely large range, they are often expressed using the logarithmic decibel scale.
The reference intensity, I₀, is normally 1 × 10-12 W/m². This value approximately represents the threshold of human hearing at certain frequencies under ideal conditions.
Typical Sound Intensity Levels
The following values are approximate and can vary with distance, environment, frequency, and measurement method.
| Sound example | Approximate level | Approximate intensity |
|---|---|---|
| Threshold of hearing | 0 dB | 1 × 10⁻¹² W/m² |
| Quiet whisper | 30 dB | 1 × 10⁻⁹ W/m² |
| Normal conversation | 60 dB | 1 × 10⁻⁶ W/m² |
| Busy traffic | 80 dB | 1 × 10⁻⁴ W/m² |
| Loud machinery | 100 dB | 1 × 10⁻² W/m² |
| Threshold of discomfort | 120 dB | 1 W/m² |
Frequently Asked Questions
Learn more about acoustic power, intensity, distance, and decibel calculations.
The SI unit of sound intensity is watts per square metre, written as W/m².
For a point source in a free field, sound intensity decreases according to the inverse-square law. If distance doubles, intensity becomes one-quarter.
The standard reference intensity used for airborne sound is 1 × 10⁻¹² W/m².
No. Sound power is the total acoustic energy emitted per second by a source. Sound intensity is the sound power passing through a specific unit area.
Yes. Select “Sound intensity level,” enter the sound intensity, and the calculator will convert it to decibels using the standard reference intensity.
The spherical spreading formula assumes an ideal point source in a free field. Walls, reflections, absorption, weather, and directional speakers can produce different real-world results.