Sound Intensity Calculator
Find sound intensity and level from power and area.
Results update as you type.
How it works
Sound intensity measures how much sound power flows through a unit area, and this calculator finds both the intensity and its level in decibels. You enter the sound power in watts and the area in square meters, and it returns the intensity in watts per square meter and the corresponding sound intensity level in decibels. Intensity is simply power divided by area, so the same sound power spread over a larger area gives a lower intensity, which is why sound gets quieter with distance as it spreads over an expanding sphere. Because the range of intensities the human ear detects is enormous, spanning about twelve orders of magnitude from the faintest audible sound to the threshold of pain, we use the decibel scale, a logarithmic measure referenced to the quietest audible intensity of ten to the minus twelve watts per square meter. The calculator computes this level so you can express intensity in the familiar decibel units. Every tenfold increase in intensity adds ten decibels, so 120 decibels, the output for one watt over one square meter, corresponds to an intensity a trillion times the hearing threshold, near the pain threshold. This is used in acoustics, audio engineering, noise control, and physics. Enter the sound power and area to compute sound intensity and its decibel level.
I = P / A; L = 10·log₁₀(I / 10⁻¹²)
Sound intensity is the sound power divided by the area it passes through, in watts per square meter. The intensity level in decibels is ten times the base-10 logarithm of the intensity divided by the reference intensity of 10⁻¹² watts per square meter, the threshold of human hearing. The decibel scale compresses the huge range of audible intensities.
Source:Acoustics
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter sound power and area.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Sound intensity updates instantly as you type — no button to press.
Frequently asked questions
What is sound intensity?
Sound intensity is the amount of sound power passing through a unit area, measured in watts per square meter. It describes how concentrated the sound energy is. Higher intensity means a louder sound at that point. Intensity decreases as sound spreads out over a larger area with distance from the source.
How is sound intensity level in decibels calculated?
Take ten times the base-10 logarithm of the intensity divided by the reference intensity of ten to the minus twelve watts per square meter, the threshold of hearing. This converts the intensity into decibels, a logarithmic scale that compresses the enormous range of audible sound intensities into manageable numbers.
Why use a logarithmic decibel scale?
The human ear detects sound intensities spanning about twelve orders of magnitude, from the faintest whisper to painful noise. A linear scale would be unwieldy, so the logarithmic decibel scale compresses this range: each tenfold increase in intensity adds just ten decibels, matching how our perception of loudness works approximately logarithmically.
Why does sound get quieter with distance?
As sound travels from a source, its power spreads over an increasing area, typically the surface of an expanding sphere. Since intensity is power divided by area, the growing area reduces the intensity. For a point source, intensity falls with the square of the distance, so doubling the distance quarters the intensity.
What intensity corresponds to common sounds?
The threshold of hearing is about ten to the minus twelve watts per square meter, or 0 decibels. Normal conversation is around 60 decibels, a busy street about 80, and the threshold of pain near 120 to 130 decibels. Each 10-decibel step represents a tenfold increase in intensity, so these differences are vast.