I recorded my class lectures. Now my recorded class lectures notes has no sound. How do i fix a no sound recorded audio?
By reshooting it.
You say now your recorded class lecture notes has no sound. Does this mean you played them back at least one time and were able to listen to them? Are these digital recordings or were they recorded to analog cassette tape? Possible causes and outcomes vary drastically depending on those things I just asked.
It is very likely that in some way you did not actually make the recording - probably some wrong setting on the device you were hoping to record on. Therefore there is no way to "bring it back from the dead" - it was never alive in the first place. Learn the lesson for next time. The night before the lecture make a brief test and listen to it through headphones etc. Then shortly before the lecture test it again just to make sure that the system is working.
If the sound wasn't recorded to begin with, there is no such thing as "recovering" it. You need to make sure, somehow, that sound is being recorded while the event is happening.
If you really didn't record the sound then you obviously can't do anything about it. But how did you record it, and how are you trying to play it - it's relatively difficult to record without sound so the problem could be that the audio's not playable rather than not there.