What is air absorption

 
 

Fill in the three input fields above and click the calculation button to display the
Calculate air absorption. This is available as additional (!) Air cushioning or Dissipation
known in the air, because the value must be the calculated usualDistance damping
(Distance attenuation, distance attenuation) of the audible sound after 1 / r law
can be added.
When entering a decimal, the is always Point to use.
 
Unfortunately, the above program does not work with "Google Chrome". Why this is so is unclear. It's the first program that doesn't work. Mozilla Firefox and Internet Explorer is OK.
 
How does the "distance from the sound source" affect the sound?
The sound level changes with distance, but there is no frequency dependence.
How does "air damping at high frequencies" affect the sound?
The sound level changes with distance, but there is a significant frequency dependence.
 
There is the usual "non-frequency-dependent attenuation" (decrease) of the sound with distance (distance attenuation or distance attenuation) and the "frequency-dependent attenuation of the air at high frequencies (dissipation)".
Both cases are to be considered separately and must therefore be calculated individually.
 
The distance-dependent and frequency-dependent air absorption can be calculated, which is known as additional (!) Air attenuation or dissipation of the air, but then the value of the calculated usual distance attenuation (distance attenuation, distance attenuation) of the audible sound must be added according to the 1 / r law .
 
 
Acoustics - attenuation of sound as it propagates outdoors -
Calculation of the absorption of sound by the atmosphere (air)

ISO 9613-1: 1993 shows an analytical method for calculating the sound attenuation resulting from the atmospheric absorption (air absorption) under different meteorological conditions. In the case of sine tones, the attenuation of air absorption is expressed as a damping coefficient depending on the frequency of the tone from 50 Hz to 10 kHz (no ultrasound), the temperature (−20 ° C to +50 ° C), the relative humidity (10% to 100% ) and the pressure (101325 Pa = 101.325 kPa) of the air. Also, the formulas for wider ranges are not explained solely for sine tones - only audible sound from 20 Hz to 20,000 Hz.


Frequency-dependent air attenuation (dB) at a distance of 30 m
at different humidity levels (percent)
 

How does the sound decrease with distance? Calculation of the distance attenuation:
Change of level Δ L with distance r

This air attenuation applies in direct field D (free field), i.e. outdoors without disturbing reflections.
When calculating the decrease in the high frequencies of speakers in the living room due to additional air absorption with distance, this formula is certainly not applicable.
In the room sound field R (diffuse field) in rooms, the laws of frequency-dependent air attenuation (dissipation of the air) cannot apply due to the reflections present.
The fluctuating air pressure does not change the sound of musical instruments in a hall or room because it does not change the speed of sound; please refer:http://www.sengpielaudio.com/Rechner-schallgeschw.htm

Composition of the air

Constant composition
(Sizes remain the same over time and place)
Nitrogen (N.2)  78,08 %
Oxygen (O2)  20,95 %
Argon (Ar)  0,93 %
Neon, helium, krypton  0,0001 %
Variable composition
(Sizes change over time and place)
Carbon dioxide (CO2)  0,039 %
Water vapor (H.2O) 0 to 4%
Methane (CH4) traces
Sulfur dioxide (SO2) traces
Ozone (O3) traces
Nitrogen oxides (NO, NO2) traces

 
Really forget about dBA when measuring air loss.
Words to bright minds: Always ask what a manufacturer has to hide when the A-frequency weighting is given.*)
 
 
*) http://www.google.com/search?q=Always+wonder+what+a+manufacturer+Rane&filter=0