Hello,(adsbygoogle = window.adsbygoogle || []).push({});

I am trying to understand how this graph http://en.wikipedia.org/wiki/File:Bandwidth_2.svg

gets plotted. My goal is to write a small program that takes the center frequency/bandwidth and a (cut/boost) gain values and plot the curve.

I initially assumed, all I needed to find was an equation of gain in terms of frequency to plot it. I have been searching for a few weeks now and I keep running into transfer functions and many different types of them. But I dont understand how this translates into a gain(yaxis) vs freq(xaxis) plot.

For example, I found the following equation at http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt

b0 + b1*z^-1 + b2*z^-2

H(z) = ------------------------ (Eq 1)

a0 + a1*z^-1 + a2*z^-2

the a0,a1,a2,b0,b1,b2 are calculated in terms of frequency/gain/bandwidth. On plotting H(z) I get something that looks like a bandpass filter curve but what does H(z) and z represent?

I dont have an electrical engineering/math background but am really interested in understanding how this bandpass curve gets drawn. Any advice on how to go about this would be greatly appreciated. Thanks!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# How to plot frequency vs gain for a filter?

**Physics Forums | Science Articles, Homework Help, Discussion**