!!!!low frequency distortion!!!!

[magus2500x]

I will work on it some more over the next few days and post the results sometime later. Arigato for the assistance.
and sorry i was online but didn't see that post

[steve]

I'm not so sure I agree, I am not saying it would necissarily be easy, but instead of looking for all the different frequencies that the distortion would be on, you would instead just try and remove a majority of the frequencies that they aren't on, which I believe, but am not possitive about, should be a little easier than going through one frequency at a time trying to find the bad ones. ...

Perhaps this will help to reveal the problem:

distortion.png (9.45 KiB) Viewed 1135 times

The top track shows a recording of some audio.

The second track shows a recording of similar audio that has suffered digital clipping - note the flat (horizontal) portions where the waveform has been clipped.

The third track is a copy of the second track after using ClipFix - note that ClipFix works very well on this kind of distortion and has simply smoothed the clipped areas by drawing the waveform higher, following the slope of the waveform either side of the clipped area to make a smooth curve

The fourth track is similar audio that has suffered distortion due to overloading the microphone. - Note that it looks quite similar to track 1, but perhaps a little more wiggly. ClipFix cannot do anything with this track as there are no obvious "clipped" areas for it to fix.

Now let's look at a plot of the frequencies.

not distorted.png (13 KiB) Viewed 1136 times

Here we see the frequencies in the "clean" recording (track 1)

distorted.png (13.39 KiB) Viewed 1135 times

And here we see the frequencies in the recording which overloaded the microphone (track 4)

Although we can clearly hear the difference (track 1 sounds clean and track 4 sounds distorted), the frequencies that occur are not very much different. Most importantly, both of these tracks contain a broad range of frequencies that cover more or less the full audio range. We can not filter out the "distorted frequencies", because the same frequencies exist in both the distorted and the clean recordings though not necessarily in the same proportions. If we try to remove frequencies that occur as a result of the distortion, we will unavoidably be removing the audio as well. Koz has previously described this sort of thing as "trying to un-bake a cake to get the ingredients".

You may notice that there is a higher proportion of high frequencies in the distorted track, and may be tempted to think that we can simply reduce the level of high frequencies to make it sound less distorted but in practice this just makes it sound dull and distorted (rather than clean).

[magus2500x]

Thank you that did help quite a bit, I did find out some more information that may help others, Most of the problem sound I found to be between 0hz and 300hz, once I cleaned that frequency up it made an 80 % improvement, I am tracking down the other frequency range that has the problem, its somewhere between 2000 and 5000hz i think towards the low end of that. I used another program to split the tracck into six different frequencies, thus I can alter just one frequency range and remove an unwanted part of it then rejoin them without altering the other frequency sets, that is something that audacity really should try and add to the program, a frequency splitter. Anyway as I continue to work on this i will continue to post more as I find it out. For now I have to redo all that I have worked on in the past three hours due to overloading my processor and crashing the program , but now I know not to run so much while working on the audio.
-T.G.MAGE