I have frequency response data. It is output from an acoustic simulator.
I convert this into an impulse response, and get:
In that picture the blue line is the impulse response. Mostly it is hiding behind the green line (which is the impulse response if I halve the frequency resolution).
I'm sorry for an unclear picture. I will replace it in due course.
Anyway, the thing I notice of interest is that if the impulse response is regarded as a loop, the ends appear to match up.
Is there any mathematical basis for this?
It seems strange to me that the impulse response is somehow non-causal. Because what it is modelling is a single pressure wave hitting a microphone. Commonsense suggests to me that it should have a very sharp attack as the main wave hits followed by diminishing ripples corresponding to echoes.
So I'm quite surprised to see ripples before the main spike, let alone before t=0, as it were.
Is this some artefact of the FFT due to the fact that it is forced to sample at discrete intervals, therefore the spike cannot be completely accurate, and maybe the preceding wobbles are compensating for this.
In which case would I do better to reposition the start of the impulse response 100 samples in from the end, and have it wrap round?