I am trying to measure the frequency response of different audio canals, e.g. tubes, hollow pipes etc.
My experimental setup looks like this: I generate an audio signal with a loudspeaker (Visaton WS 17 E 4 Ohm, datasheet: Datasheet loudspeaker which then passes through my device under test (e.g. the tube) and is then measured by a microphone (with a flat frequency response).
Unfortunately the output of my loudspeaker when measured directly (without the device under test in between) does not show a somewhat flat frequency response, on the contrary I see something like this. To obtain the graph I apply basic FFT to the output data of the microphone.
The input signals I am using are sine sweeps and white noise. Both results in very similar results. The same applies to the audio amplifier I am using, switching to a different one changed nothing. I therefore do not believe these two to be the issue.
I wonder now what I can do to obtain sensible results after the FFT. Do you have an idea how I can either improve the output of my loudspeaker respectively what causes the peaks and valleys in it? Alternatively, is there a way to kind of "subtract" the frequency response mathematically to obtain clean results?
I am very much looking forward to hearing any suggestions because I have already invested a lot of time and I am running out of ideas.