[LAD] sound dissipation in air - formulas and filters?

[victor]

you can try using a bank of equaliser filters in parallel? The
Regalia and Mitra design ("Tunable Digital Frequency Response Equalization
Filters", IEEE Trans. on Ac., Sp. and Sig Proc., 35 (1), 1987) works
quite well.

Victor
----- Original Message ----- 
From: "Jörn Nettingsmeier" <nettings at folkwang-hochschule.de>
To: "The Linux Audio Developers' Mailing List" 
<linux-audio-dev at lists.linuxaudio.org>
Sent: Friday, January 30, 2009 8:15 PM
Subject: [LAD] sound dissipation in air - formulas and filters?


> hi everybody!
>
>
> does anyone know a way to compute filters that simulate air dissipation
> for a given temperature and humidity?
>
> so far, all i've found is an online calculator at
> http://www.sengpielaudio.com/calculator-air.htm, but the javascript in
> there is not exactly fit for citation :)
> plus i know there is a standard (ISO 9613-1:1993) that deals with sound
> attenuation, but i don't have access to a standards library and don't
> feel like buying it...
>
> a rough calculation at 18°C and 85% relative humidity (using sengpiel's
> tool) yields:
>
> f[Hz] dp[dBSPL/m]
> ----------------------
> 20 0
> 40 0
> 80 0
> 160 0
> 320 0.001
> 640 0.003
> 1280 0.006
> 2560 0.011
> 5120 0.032
> 10240 0.112
> 20480 0.404
>
> which indicates that for my usecase (close-miked sounds that need to be
> placed at distances between 10 and 45 m), the air-damping non-linearity
> is really important.
>
> question is: how do i design a filter to simulate this? would make a
> cool ladspa tool eventually...
>
> pointers to related papers or maybe even filters are most welcome.
>
> best,
>
>
> jörn
>
>
>
>
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