Guess the frequency response of a filter with little information I have a processing unit that does a nice EQ filtering on soundfiles.
The only thing I can do is : I give the original .wav file, and the processing unit gives me back the filtered .wav. I have no other information than this.

I'd like to know the frequency response graph of this processing unit. How to do it ?


1) feed the unit with a "flat spectrum white noise", and see the spectrum of the filtered file? It works but it is not very accurate
2) feed the unit with sinewaves soundfile with frequency = 20, 30, 40, 50, etc... 20 000 Hz.
Then I examine the response for each file... and I can draw a frequency response graph after 10 hours of work :)
3) feed the unit with a frequency sweep ?  and then try to see what's the unit's reponse to this sweep ? How to decode the response into a nice frequency response graph  ?
4) I imagine that there is another better solution?


Thank you.
If you know that the system is linear and time invariant, the easiest method (assuming that you have no noise added in the process) is to let the system act on an impulse function. The Fourier transform of the output is the frequency response of the system.