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| 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 audible 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 from 50 Hz to 10 kHz (no ultrasound), 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 and for other than pure tones - only audible sound. It is often asked what formula stands for the calculation of the damping of air: Formula for calculating the air damping up to 10 kHz |
| Frequency dependent attenuation of air (dB) in 30 m distance at different humidity (percent) |
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How does the sound decrease with increasing distance? 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. The changing of atmospheric pressure does not change the sound of musical instruments in a concert hall or in a room, because the speed of sound does not change; see: http://www.sengpielaudio.com/calculator-speedsound.htm |
Composition of air
| Constant configuration (Values stay equal over time and place) |
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| Nitrogen (N2) | 78.08 % |
| Oxygen (O2) | 20.95 % |
| Argon (Ar) | 0.93 % |
| Neon, helium, krypton | 0.0001 % |
| Variable configuration (Values change over time and place) |
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| Carbon dioxide (CO2) | 0.039 % |
| Water vapor (H2O) | 0 to 4 % |
| Methane (CH4) | traces |
| Sulfur dioxide (SO2) | traces |
| Ozone (O3) | traces |
| Nitrogen oxides (NO, NO2) | traces |
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