Calculation: absorption of sound by the atmosphere air - sengpielaudio
 
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Damping of Air of High Frequencies (Dissipation)

Calculation method of absorption of sound by the atmosphere
depending on the damping as a function of frequency, temperature, and humidity
Acoustics - Attenuation of sound during propagation outdoors - ISO 9613-1:1993

Temperature of air:  °C   °F
Relative humidity:   %
Frequency:   Hz
   
                ↓                     
   
 Atmospheric absorption:   dB/m    dB/100 m    dB/100 ft 
Fill the known values in the three enter boxes and press the calculate bar to calculate the
air absorption. This is the "added" air damping (dissipation of air), because this value
must be added to the usual distance damping of sound after the 1/r law.

Acoustics - Attenuation of sound during propagation outdoors -
Calculation of the absorption of sound by the atmosphere
ISO 9613-1:1993 specifies an analytical method of calculating the attenuation of sound as
a result of atmospheric absorption for a variety of meteorological conditions. For pure-tone
sounds, attenuation due to atmospheric absorption is specified in terms of an attenuation
coefficient as a function of the frequency of the sound (50 Hz to 10 kHz), the temperature
(-20 °C to +50 °C), the relative humidity (10 % to 100 %) and pressure (101325 Pa =
101.325 kPa) of the air. Formulae are also given for wider ranges (e.g. ultrasonic
frequencies, lower pressure) and for other than pure tones.

Calculation of distance damping: Changing of the sound level Δ L with the distance r

This air absorption is valid for the direct field D (free field), an outside location without
contributing reflections. When calculating the additional high frequency attenuation of
speaker signals in a living room caused by air absorption this formula (method) cannot to
be used. Due to the additive reflections in the room field R (diffuse field of a room) the law
of frequency dependent air damping does not apply.

Composition of air

Constant configuration
(Values stay equal over time and place)
nitrate (N2) 78.08 %
oxygen (O2) 20.95 %
argon (Ar)   0.93 %
neon, helium, krypton   0.0001 %
Variable configuration
(Values change over time and place)
carbon dioxide (CO2)   0.0003 %
water vapor (H2O)   0 − 4 %
methane (CH4)   traces
sulfur dioxide (SO2)   traces
ozone (O3)   traces
nitrogen oxides (NO, NO2)   traces

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