Arcline 8/212 User Guide V1.0
Page 57
More about air absorption coefficient
Here’s a graphical representation of the sound absorption mechanisms mentioned on the
previous page:
Figure A.12: Graphical representation of atmospheric sound absorption at 20% RH, 20ºC and 1.0 atm
(The Green lines & text box show the 21.7 dB/100 m (vertical axis) loss predicted for 8 kHz (horizontal axis) at 20% RH and 20°C)
Note that this is only a snapshot. The resultant slope varies -mainly with relative humidity and
temperature for typical concert or festival conditions - and only slightly with atmospheric
pressure unless you’re working well above sea level or under extreme weather conditions!
Air absorption calculators
The author uses a Wolfram Computable Document Format (CDF) player running a CDF object
designed by Prof. Dan Russell of The Pennsylvania State University to calculate air absorption.
The illustration above is a marked-up screen shot from the programme.
See www.acs.psu.edu/drussell/Demos/Absorption/Absorption.html for free laptop software
and CDF file.
Note that Void Acoustics cannot be responsible for non-Void applications. Use at
your own discretion!
There are many more on-line calculators and some phone apps that include an air absorption
calculator. One of the most popular general-purpose audio, lighting and electrical calculator
“toolkits” is Doctor ProAudio’s PAcalculator. It’s available on-line at www.doctorproaudio.net
along with other useful stuff.
A phone app is also available. See www.doctorproaudio.com/doctor/calculadores_en.htm.
11 Appendix A - Line array basics
Summary of Contents for Arcline 212
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