Re: equal loudness calculation (Julian Rohrhuber )


Subject: Re: equal loudness calculation
From:    Julian Rohrhuber  <rohrhuber(at)UNI-HAMBURG.DE>
Date:    Mon, 18 Apr 2005 21:37:06 +0200

At 12:54 Uhr +0200 18.04.2005, Jose-Javier Lopez wrote: >> in this case, I don't want to filter a sound, but simply scale its >> amplitude. >> Or is there a way to make the formula itself efficient by >> implementing it as a filter? > >If you have your data in freq domain, just use the equation for weighting. >In this case you don't need to filter in time domain. ok, that seems good. if anyone else needs it, here is the formula mapping freq to amp: ( var k = 3.5041384e16; var c1 = pow(20.598997,2); var c2 = pow(107.65265,2); var c3 = pow(737.86223,2); var c4 = pow(12194.217,2); {|f| var r = pow(f,2); var m1 = pow(r,4); var n1 = pow(c1 + r, 2); var n2 = c2 + r; var n3 = c3 + r; var n4 = pow(c4 + r, 2); var level = k * m1 / (n1 * n2 * n3 * n4); sqrt(level) }; ) >JJ > > > >----- Original Message ----- >From: "Julian Rohrhuber" <rohrhuber(at)UNI-HAMBURG.DE> >To: <AUDITORY(at)LISTS.MCGILL.CA> >Sent: Monday, April 18, 2005 12:18 PM >Subject: Re: [AUDITORY] equal loudness calculation > > >> >This is the analitic equation for A-Weighting. >>> >>>http://www.beis.de/Elektronik/AudioMeasure/WeightingFilters.html#A-Weighting >> >> >> thank you, this is quite exactly what I was looking for. >> >>>Just, pass it to Z domain and use "a" and "b" coef. in a IIR filter. >> >> in this case, I don't want to filter a sound, but simply scale its >> amplitude. >> Or is there a way to make the formula itself efficient by >> implementing it as a filter? >> >>>Very efficient ! >>> >>>JJ >>> >>> >>> >>>----- Original Message ----- From: "Julian Rohrhuber" >>><rohrhuber(at)UNI-HAMBURG.DE> >>>To: <AUDITORY(at)LISTS.MCGILL.CA> >>>Sent: Tuesday, April 12, 2005 4:25 PM >>>Subject: [AUDITORY] equal loudness calculation >>> >>> >>>> I'm looking for a computationally efficient way to do a frequency >>>> dependent amplitude compensation. The emphasis is much less accuracy >>>> (especially not for different loudness levels) but more a reasonable >>>> approximation - maybe a polynomial. >>>> >>>> Any hints? >>>> >>>> -- >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> . >>>> >> >> -- >> >> >> >> >> >> >> >> >> . >> -- .


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Electrical Engineering Dept., Columbia University