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*To*: AUDITORY@xxxxxxxxxxxxxxx*Subject*: Re: equal loudness calculation*From*: Julian Rohrhuber <rohrhuber@xxxxxxxxxxxxxx>*Date*: Mon, 18 Apr 2005 21:37:06 +0200*Delivery-date*: Mon Apr 18 15:46:20 2005*In-reply-to*: <00f001c54404$f828ab60$33212a9e@Neutrino>*References*: <f06200720be8189f1a41f@[134.100.43.234]> <001d01c543f2$07902140$33212a9e@Neutrino> <f06200731be8939a9f49f@[194.95.161.215]> <00f001c54404$f828ab60$33212a9e@Neutrino>*Reply-to*: Julian Rohrhuber <rohrhuber@xxxxxxxxxxxxxx>*Sender*: AUDITORY Research in Auditory Perception <AUDITORY@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx> To: <AUDITORY@xxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx> To: <AUDITORY@xxxxxxxxxxxxxxx> 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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**Follow-Ups**:**Pitch and Music***From:*Vidya Ganesh

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**Re: equal loudness calculation***From:*Jose-Javier Lopez

**Re: equal loudness calculation***From:*Julian Rohrhuber

**Re: equal loudness calculation***From:*Jose-Javier Lopez

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