I'm trying to create a equalizer (in JAVA) and I made few assumptions but I'm not sure if I'm true or false about the use of the filters. Here is the list of the points I'd like to check.

1/ I'm applying the continuous transfer function (low-cut, high-cut or passband filters) to a sampled signal. As my sampled signal have a plot each 20 Hz for example (= my spectral precision), I don't care about the value of the transfer fonction for the band 315 Hz : I will only use the value at 300 Hz or 320 Hz given by the transfer function. Is it correct ?

2/ I want to modify the gain of the signal around a frequency (central frequency +- quality factor) so, I'm using the modulus of the transfer function. My signal frequency is a complex and multiplying a complex by a real coefficient (the modulus) will change the amplitude but not the phasis (argument). Is it correct ?

3/ It was the trickyest point. Which value do I have to apply to the "K" (gain) factor of the tranfer function to sculpt my signal ? I my mind, if gain=1, I should get the signal without any transform. But if K=1 in the transfer function, I will get an attenuation outside of the passban and a "native" signal inside the passband. So, I decided to add "1" to my calculated gain and to allow negative values to the gain.

So, for example, if K=0 => gain = 1 everywhere ; if K=1 => gain = 1 outside the passband and goes until +2 (+3db) inside the passband ; if K=-0.5 => gain = 1 outside the passband and decrease until -0.5 (-3db) inside the passband. Does this calculation assumption seems correct ?

Note : the modulus of the transfer function I'm using for the passband filter is :

|H| = K / (1 + Q^2.(x - 1/x)^2 )^0.5 with K = gain, Q = quality factor, x = signal frequency / central frequency

Thank you to have read my question and thank you for all your answers.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.