Isolation Room Design Calculator

Calculate outdoor sound propagation from a noise source to a receiver. Models geometric spreading, ground effects, and atmospheric absorption (ISO 9613).

Inputs

Source sound power (dB)

Distance to receiver (m)

Frequency (Hz)

Source type (0=point, 1=line)

Ground type (0=hard, 1=mixed, 2=soft)

Temperature (°C)

Relative humidity (%)

Tab to move between fields

Results

SPL at receiver (dB)

Geometric spreading (dB)51

Ground effect (dB)-3

Atmospheric absorption (dB)0

Total path loss (dB)48

Absorption coeff (dB/m)0

How to Use This Calculator

Enter Source sound power (dB), Distance to receiver (m), and Frequency (Hz).
Set Source type (0=point, 1=line), Ground type (0=hard, 1=mixed, 2=soft), and Temperature (°C).
Adjust Relative humidity (%) as needed.
Review the SPL at receiver (dB) result.
Use Geometric spreading (dB) and Ground effect (dB) to inform your decision.

How the result changes with Source sound power (dB)

Source sound power (dB)	SPL at receiver (dB)
16	-32
56	8
104	56
144	96

What each input means

Source sound power (dB): Sound power level of the source in dB re 10⁻¹² W. Typical: car horn ~105, truck ~100, HVAC unit ~90.
Distance to receiver (m): Distance from the source to the receiver in meters.
Frequency (Hz): Sound frequency. Atmospheric absorption increases significantly at higher frequencies.
Source type (0=point, 1=line): 0 = Point source (single machine, speaker). 1 = Line source (road, railway).
Ground type (0=hard, 1=mixed, 2=soft): 0 = Hard (concrete, water). 1 = Mixed. 2 = Soft (grass, soil, snow).
Temperature (°C): Ambient temperature in degrees Celsius. Affects atmospheric absorption.
Relative humidity (%): Relative humidity percentage. Strongly affects atmospheric absorption at high frequencies.

What each result means

SPL at receiver (dB): Predicted sound pressure level at the receiver location.
Geometric spreading (dB): Sound reduction due to geometric spreading (inverse square law for point source).
Ground effect (dB): Additional attenuation or amplification from ground reflections. Negative = amplification.
Atmospheric absorption (dB): Sound absorbed by the atmosphere over the propagation distance.
Total path loss (dB): Sum of all attenuation factors from source to receiver.
Absorption coeff (dB/m): Atmospheric absorption coefficient per meter at the specified frequency and conditions.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Source sound power (dB) = 100, Distance to receiver (m) = 100, Frequency (Hz) = 500, Source type (0=point, 1=line) = 0 = 7 input(s) provided
Calculate SPL at receiver
SPL at receiver = sourcePower - totalLoss
52 = 52
Calculate Geometric spreading
Geometric spreading
51 = 51
Calculate Ground effect
Ground effect
-3 = -3

Engine last updated July 11, 2026. Checked against 2 independently-derived tests — how we verify calculators.

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