Repairing Damaged Audio

One of the big advantages of DSP is, the ability to separate, filter, amplify or attenuate sounds that are very close to each other in frequency.

Something that cannot be achieved using just EQ, at least not without changing the overall sonic characteristics of the clip.

Consider the plots below, by storing the samples in buffers and manipulating them with a FIR, more
precise control is then possible.
Note how harmonics and other unwanted sounds can be controlled in either amplitude, frequency, or both.

Like wise, we have full control over amplitude, sample by sample.

Extremely handy for using on clipped or otherwise distorted sound.

This has many applications in cleaning up audio, that would otherwise sound terrible,
be distracting to the listener or just down right un-usable.

Consider this first example, you are recording some outdoor ambience sounds and a freight train 
starts blowing it's hooter, something you really didn't want.

PauloV · WithTrain

You now have two options:

- Re-record (not always possible).

- Apply some DSP magic.

Here is the same clip, with no hooter.

Note how little change there is to the original quality of the clip.
Small artifacts can easily be masked with a bit more FX, equalization  or music if appropriate.

PauloV · WithNoTrain

In my next entry, will post more "before and after" examples.

Click for Part 2 Here