[LAD] Re: pd lop~ and hip~

On Tue, Apr 15, 2025 at 01:43:10PM +0200, Fons Adriaensen wrote:
> 
> Now, to be 'constructive', the correct way to compute c
> would be
> 
>    f = cutoff_frequency / sample_rate;
>    a = 2 * (1 - cos (2 * pi * f);
>    c = (sqrt (a * (a + 4)) - a) / 2;
> 
> 
> A good approximation (less than 1% relative error) 
> for 0 <= f <= 0.5 could be
> 
>    c = 2 * pi * f * (1 + f * (3.45f + 4.27f * f));

Can you explain how you get there, in terms that a 35-years-ago Straight-Cs highschool maths student might understand?

I know how algebra works and kind of how to make calculus work, and enough DSP to be dangerous, but that's about it.

-- 
Gordonjcp
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