Maybe the use of other software can add some quality to the process.

I have used one software (Bitmaps & Waves) and I am not sure if I use this software with the optimal settings.

I found another software : Praat . It seems powerful but I didn't use it because it is not as straightforward as Bitmaps & Waves

http://person2.sol.lu.se/SidneyWood/praate/frames.html

If you find another software, please let me know.