Hello guys,

I have some problem on calculate the Peaking and Notch filter.

In SigmaStudio wiki ( SigmaStudio Wiki ), I can not get both filter formula information,

and I reference the Robert Bristow-Johnson Audio Cook Book website (This : http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt)

I found that the cook book contain the peaking filter formula, but I am not sure the value "alpha" what the calculation formula is. And I follow the cook book to generate the formula in my excel, I found the final value which I got is different with the SigmaStudio capture window value. So I want to ask,** does there have the formula for the Peaking Filter and the Notch filter?** because I have some function need to use IIR filter to implement.

Please help me, thanks!

Best Regards,

Alvis.

Hello Alvis,

Try the attached spreadsheet which calculates the coefficients for a variety of filters. You can use the formulas in its cells to write C code (etc.) for your own coefficient calculations in your microcontroller. The easiest way to test the coefficients is to type them into the IIR Coefficient entry for a General Second-Order Filter, as shown below. This example tests the coefficients for a 1 KHz, Q = 10, 6 dB gain Peaking filter.

Remember to flip the signs of the

acoefficients when programming your own safeloads. SigmaStudio does this for you, which is reflected in the Capture Window.Best regards,

Bob