In the following blog post, I will help you understand a basic three part process for audio restoration. In the embedded video, I exhibit an audio file that was lifted from a video which is in need of some audio restoration. The video walks you through the process which varied from video to video in this video training set.
The first step is to either compress the audio increasing the gain during the process or removing any unwanted distortion; whichever you feel is best to lead with. You can try one process first then the second. Worse case you can apply the processes in opposite order if your initial results are not up to your expectation.
Varying the order which filters and noise reduction are applied is how a forensic examiner will proceed when restoring an audio file. Audio restoration takes time, patience and good critical listening skills.
The three filters I will demonstrate in this video are wave hammer, equalization and noise reduction. I use Sony Sound Forge software 9.0 for this example. Other audio software programs can be used and more than likely include similar filters to those found in Sound Forge.
?photo credit: Mixer Controls: Sliders Faders Buttons Switches Knobs via photopin (license)