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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