In working on the time-scale audio modification program component for this project, Prof Sullivan suggested I start in Matlab and write a program that can read an audio file, break the signal into its wavelet components, and reconstruct the signal from its wavelet components. I played around with this. In the wavelet decomposition at levels 2 and 3, the reconstruction sound was faster, thinner, and of considerably higher pitch. Wavelet decomposition at level 1, however, allowed for a reconstructed signal that sounded the same as the original. This is true for ‘db2’ and ‘db1’ wavelet types – we will be using ‘db2’ since it is biorthogonal and our design report details why we chose a biorthogonal implementation. I completed this task this week.
In addition, I worked on a STFT based phase vocoder in Matlab. I was able to successfully test time-scale audio modification through this method with simple one layered musical signals. There were no interfering audio artifacts after the modification of the signals. Having this done means that 1. I can use this phase vocoder implementation as an example as to how to integrate the DTCWT in place of the STFT, and 2. the backup plan for how we would modify the signals is complete in Matlab.
Next steps are to test these on more complex signals, and implement the phase vocoder with DTCWT.