I am trying to implement a method for measuring the response of a loudspeaker in a room using a log sine sweep stimulus.
To check my method: 1. I create the stimulus using:
Make recording length long enough so that the measurement falls towards zero (or below the noise floor)
Window the signal, and zero pad the stimulus to equal the same length as the measurement signal.
Take FFT of both stimulus and measurement
Multiply the measurement and stimulus by the inverse filter:
Shift the FFT results to order them in the ‘natural way’
Divide the FFT of the measurement signal by the reference signal
Perform inverse FFT of the division to get back to the time domain. This will be the impulse response.
I can plot this and obtain something resembling an impulse response, however there are 2 ‘mirrored’ response signals here. Resulting in what looks like 4 impulse responses. I would expect to have a symmetrical impulse response, however this has thrown me. At all points in my method I use the full symmetrical signal and do not discard any data.
Please can someone confirm if I have missed a step or misunderstood along the way?