ATAcoustic Toolbox

Propagation

Atmospheric Absorption

Explore frequency-dependent attenuation in air according to ISO 9613-1:1993.

Calculation

Climate A

Primary

Climate comparison

Selected frequency1 kHz
Absorption coefficient—
Attenuation over distance—
Remaining level—

Absorption coefficient over frequency

Select a plotted point to update the detailed result.

Climate A

Attenuation over distance

Representative frequencies for climate A; distance is shown logarithmically.

Band values

Enter up to three reporting distances.

Frequencyα100 m500 m1 km

Why air absorbs sound

Part of a sound wave's energy is converted into heat by molecular relaxation processes in oxygen and nitrogen. The effect depends strongly on frequency and atmospheric conditions. It is usually small at low frequencies but can become important at high frequencies and long propagation distances.

Calculation

ISO 9613-1 defines the pure-tone atmospheric attenuation coefficient α from frequency, temperature, relative humidity and static pressure. Total atmospheric attenuation is:

Aatm = α · d

This tool isolates atmospheric absorption. It does not include geometrical spreading, ground effects, screening, reflections or meteorological refraction.