Is there a way to remove robot-like echo from voice?

Special Interest Groups Audio Processing
1

This is part of a dialogue recorded in a meeting that happened online on a VoIP audio conference service. The audio quality is really good for all participants, but there is one person whose voice sounds like it is on auto tune, he sounds like a robot, and there is an echo, too. I have looked everywhere and have not found any satisfactory way to remove this noise and clean up his voice. Noise removal removes everything, not just the noise. If you can point me in the right direction, that would be fabulous! I am attaching a sample (voice-with-echo.wav - 723 Kb)

2

That’s not noise. That’s the echo cancellation trying to suppress an extreme delay in that branch of the conversation…and failing. There might even be a little compression junk in there. There is a real problem with communications like this that the person who sounds like garbage can’t tell unless somebody complains to him. The two directions are completely separate and his reception from everybody else is probably perfectly fine.

If that person is on DSL, then the upgoing voice can be completely destroyed, but the downcoming show is perfect. That’s called Asymmetric DSL. I have that and it drives me nuts. On a bad day, my download speed will do HiDef television, but my upload speed is just above dialup.

We urge locations where there is only one person in the room to wear headphones. Even some of the more complex videoconference connections wear headphones to help with slap, echo, and gargling. We do this kind of thing around the earth – 12 time zones – and the sound problems can get horrendous.

And you’re stuck with the quality. I don’t know of any filters that will even help a little.

Koz

3

What about hyperexpanding a copy and spectrally subtract it from the original (using Kn0ck0ut) ?, e.g. …

It’s a little better.

Update: it just occurred to me an expander would be a simpler way of achieving the same effect:
reducing the volume of the part of the waveform which is below a threshold.
hyperexpand plugin for Audacity.zip (521 Bytes)

4

Thanks very much Kozikowsky for your comments. It was helpful to understand what is going on that is causing the problem.

Trebor, thanks for the tip and for the sample. It is indeed a little better. I downloaded the plugin and I am going to try to figure out how to do what you suggested.

Thanks a lot, folks, you are very helpful!