title: Fast Fourier Transform with negative amplitude
body: <p>Using wavesurfer to analyse bird songs data and getting negative amplitudes with the FFT analysis that I can not find the reason why.</p>
  
  <p>I have been using wavesurfer for analysing my paper data on birds song. I open my data with the spectrogram and then in spectrum section is possible to find frequency and amplitude (using FFT analysis). My amplitude is negative but I can not find a way to justify that. I dont know why is that and I have significant results on my data, meaning that everything needs to be justified. The forum of the software does not work and there is literally no answer to my question on the internet. I have even emailed the creators asking for help. Find a screen attached to the windows.</p>
  
  <p><img src="https://i.stack.imgur.com/DE0Xt.png" alt="plot showing -60.1 dB amplitude"></p>