Removing distortion

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Removing distortion

Permanent link to this post Posted by Elrich » Mon Jan 29, 2018 2:14 pm

One of the contributors to my podcast sent me an interview he recorded in Skype. I'm surprised he didn't notice it, but every time his interviewee speaks, there's distortion. It sounded to me as if he had placed a mic in front of a rattly speaker, but he says he recorded with the Skype recoder plugin.

I found a video online that recommended using Clip Fix (under Effects) to fix distortion, but it didn't make much difference. Is there something else I can do in Audacity to smooth out the sound? It's hurting my ears to listen to this interview.
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Re: Removing distortion

Permanent link to this post Posted by kozikowski » Mon Jan 29, 2018 6:22 pm

It's hurting my ears to listen to this interview.

And would probably hurt our ears if we could hear it. We need to experience it to guess at a solution. Post a WAV clip of the work on the forum. If it's stereo (two blue waves) post 10 seconds. Mono, 20 seconds. We can't do anything with a two second blast of trash.

Scroll down from a forum text panel > Upload attachment > Browse.

viewtopic.php?f=49&t=72887

Koz
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Re: Removing distortion

Permanent link to this post Posted by Elrich » Mon Jan 29, 2018 11:12 pm

Exactly. I'm afraid nobody's going to be able to get through it.

Here's a clip.
Attachments
180205sample.wav
(1.63 MiB) Downloaded 5 times
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Re: Removing distortion

Permanent link to this post Posted by kozikowski » Mon Jan 29, 2018 11:41 pm

This is after extensive surgery.

This is odd. Analysis of the original proves there are no tones higher than 7500 Hz. None. The musical tonal population of the clip goes out to about 7500 and drops as a rock. That's significant because AM radio goes away at 5000. So the best this clip will ever do is slightly better than your local AM radio station. And it's distorted, I'm guessing from simple overload.

So that's all I can do. I eliminated all the tones higher than about 2500 (worse than a telephone) and that got rid of most of the harsh crispness. It is actually better because I can understand what's being said.

Whoever shot this should find a different recording technique and pay attention to the volume.

Koz
Attachments
180205samplePatched.wav
(1.63 MiB) Downloaded 4 times
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Re: Removing distortion

Permanent link to this post Posted by kozikowski » Tue Jan 30, 2018 12:25 am

Skype recoder plugin.

Can you blow that out a little? Which software exactly on what kind of machine? Links? Has it ever worked or is this the first pass?

That didn't come from Skype, did it? Recording Skype is a major battle. They change their technology on occasion and even pay-to-play Windows software like Pamela occasionally loses it.

You can record Skype with perfect reliability. All it takes is two computers, or one Skype computer and a sound recorder. Basically, that's how all the grownups do it. That's how the networks manage to get good Skype interviews day after day after day.

I did it with two older Macs.

Image

Pando does it with a much larger setup, but if you strip off all the stuff you don't really need, like their scheduling and research computers, it's down to two computers and a sound mixer, and most of the mixer isn't being used.

Image

What's key is recording Skype on a different machine than the one running Skype. However you get there, that's critical.

I know people are going to say, "My cousin in Tallahassee gets this to work reliably every time on one machine."

Or they do until Skype changes their algorithm, or worse, their setup is a celebrity unicorn. There is only one of them in the country. We had a unicorn post on the forum once. Nobody else could get it to work the way he had it. It doesn't count unless everybody can do it.

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Re: Removing distortion

Permanent link to this post Posted by Elrich » Tue Jan 30, 2018 9:53 am

kozikowski wrote:This is after extensive surgery.

This is odd. Analysis of the original proves there are no tones higher than 7500 Hz. None. The musical tonal population of the clip goes out to about 7500 and drops as a rock. That's significant because AM radio goes away at 5000. So the best this clip will ever do is slightly better than your local AM radio station. And it's distorted, I'm guessing from simple overload.

So that's all I can do. I eliminated all the tones higher than about 2500 (worse than a telephone) and that got rid of most of the harsh crispness. It is actually better because I can understand what's being said.

Whoever shot this should find a different recording technique and pay attention to the volume.

Koz


Koz, that does sound better. What did you use? The Low Pass Filter? I tried that just now but it didn't seem to have much effect.
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Re: Removing distortion

Permanent link to this post Posted by Elrich » Tue Jan 30, 2018 9:57 am

As I've already explained, it did come from Skype, but not recorded by me, and actually recorded on a different continent from where I am. I'm told it was recorded from Skype using the recorder plugin, but I've never had such bad results using that, and I've recorded hundreds of podcast episodes from Skype.

Multiple machines, not doable on my budget, but as I say, I've never gotten this kind of result on ones that I've recorded.
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Re: Removing distortion

Permanent link to this post Posted by kozikowski » Tue Jan 30, 2018 11:37 am

I need to go back over the tools to remember what I did (different machine).
I've never gotten this kind of result on ones that I've recorded.

How? I've wondered why Skype doesn't have a button you push to record the conversation. Everybody on earth wants that button.

We're assuming the performer's microphone was working OK? I bet it wasn't. It sounds like what happens when somebody plugs a sound mixer, not a microphone, into the MIC-IN of a laptop. Very great mismatch.

Because of digital and encoding delays, nobody has sidetone any more like older telephones did. You never get to hear what you sound like. Your first clue that your own voice is a distorted mess is someone will comment they can't understand you and you need to call back.
I'm surprised he didn't notice it,

Are you the Producer? Do you decide what goes into the show? You need to have a nice chat with the recordist. They can't submit voices that sound like five miles of bad road.

I'm looking for the settings.

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Re: Removing distortion

Permanent link to this post Posted by Elrich » Tue Jan 30, 2018 11:39 am

Yes, I'm the producer, although often I'm a participant as well. This same contributor has done other interviews that didn't sound bad.

He says that the interviewee was talking on Skype via his phone, and that that was probably the source of the problem. Probably not a good mic on his phone.
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Re: Removing distortion

Permanent link to this post Posted by kozikowski » Tue Jan 30, 2018 11:47 am

First I removed low pitched rumble with Effect > Equalization: Low rolloff for speech, Length about 5000.

Then Effect > Low Pass Filter: 2500, 24dB. That's a pretty stiff filter.

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