I do some part-time work editing recordings of live radio broadcasts for podcast. The radio station is community-run so there are plenty of problems to deal with!
Recently the station did a broadcast of a live concert which they attempted to record. Due to other commitments I wasn’t able to attend or advise them on the best way to do this. I was told that it wasn’t possible to record live at the venue so they made a recording (I’m not sure how) back in the studio as the show was being broadcast. Unfortunately, the recording contains what sounds like electronic feedback which is causing fairly rapid discrete echoes. They’re all through the recording (three hours worth!).
Any thoughts on whether this recording can be improved in any way? Personally, I’ve got my doubts. As it stands, I don’t think the recording is salvageable which is a great shame.
I’ve attached a short excerpt containing dialogue only which shows the problem.
The short answer is that the damage is permanent and irreparable.
The immediate problem for any echo cancellation / deconvolution technique is that you don’t have either “dry signal alone” or “impulse response alone”, you only have a mix of signal and echo and no good way to know which is which. It’s fairly easy to see that the primary echo is about 97 ms, but that is not really good enough to perform effective echo removal.
Based on a 97 ms delay I managed to achieve a little reduction in the echo, which you can hear by comparing this version with the original: