Blank audio when uploaded for podcast

I edit my podcast using Audacity. For transition clips between segments, I often splice in clips I grabbed using Clip Grab off of YouTube. Sometimes when I grab these clips they are downloaded in m4a format, but they show up fine and I am able to edit them.

When I finalize the podcast episode on my computer, everything sounds fine. However, then sometimes when people listen to the podcast on their podcast app or in iTunes, the spots where there is supposed to be the YouTube clips between segments are nothing but dead air.

Does anyone have any idea why it may happen? Is it the m4a format causing the error? And if so, why does the file play totally fine after I export it as an MP3 on my computer, but then have the dead spaces where I spliced in the clips on someone else’s computer or podcast app?

Thank you!

Also I’m using Audacity 2.1.0. Just realized that’s out of date so I’m updating. Maybe that was the issue?

Okay, and another update on the issue!

It turns out that some clips that I spliced in but kept in the SAME track DO play. However, the clips that I spliced in by putting them on a DIFFERENT track (because there is some overlap) are the ones that are NOT playing. The clips that aren’t playing are in the top track, if that makes any difference.

What in the world is going on? After I export it all to an MP3, why would it play fine on my computer, but then not play when MULTIPLE people (not just one, so it’s not some one off issue) tried to play it on their computer?

The top track was muted at the time you exported the audio?

Unfortunately, you can’t check that after the facts…

No, they weren’t muted. I would have noticed it being greyed out.

I did have the volume turned down. But I still don’t understand why it would play on my computer, but it wouldn’t on someone else’s when we are both using THE SAME website, and clicking THE SAME play button (episode 31 at 13:30 mark and 36:30 mark):

In any case, I tried re-mixing it and reduced the top track’s volume through the Amplify plugin, rather than the volume toggle on the track itself. Hoping that fixes the problem.

Here we see two versions of your podcast. The upper stereo track is your podcast as downloaded from your site. Below it is the same file, but mixed to mono.
As you can see, there are places in the second version where the show almost disappears. The reason for this is that the left and right channels of the original stereo track are “out of phase”. If we zoom in really close, we can see what that means. The upper (left) channel and the lower (right) channel of the stereo track are virtually identical, but “upside down” from each other (technical terms: “inverted” or “180 degrees out of phase”). When the two channels are added together (“mixed”) to mono, the two waveforms cancel each other out (they sum to zero).
Mixing to mono is what usually happens when listening to a stereo show via a mono playback system. For anyone listening in mono, parts of your show “sum to zero”, meaning that they mix down to silence.

Oh my gosh thank you so much! This has been driving me crazy.

How do I prevent the left and right channels from getting “out of phase” in the future for anyone who might listen in mono? I’m not sure why it happened in that part of the file when I pasted in those clips.

Actually, in a full stereo music system, those small portions will not sound perfect and normal. They might sound like they’re slightly weird or coming from behind you.

This is a channel test I recorded including an “out of phase” segment. It’s 39 seconds.

Open that in Audacity and you can hear what it sounds like when I flop the channels as part of the demonstration.

I’m going to go back and read through that again, but it’s possible the on-line segments were recorded wrong. That’s really easy to do if you have a half-professional and half-home style recording system. As as you noted, if you’re only listening in stereo you might not catch it.


Go back and download one of those YouTube segments and open it up in Audacity cold before you do anything to it. Magnify the blue waves like crazy so you can get down to the individual sample dots. Are they the same or opposite?

If it’s a good stereo show, the waves will not be the same, but they should go mostly the same direction. Find a portion with a solo singer. Those should show up better.


My guess is that those clips had the problem before you pasted them.
Where did you get those clips? Do you still have the original versions?

I downloaded the clips off YouTube using ClipGrab. I attached a short snippet of the audio (after I exported it as an MP3) and screenshots of the file in Audacity.

I also took a screenshot of the menu when I click on the filename on the track. I have just noticed that “Left Channel” is checked, but the option is greyed out so I cannot uncheck it. However, in my headphones the audio still does come out of both the right and left.

Is there something I can do, such as “Swap Stereo Channels” or “Split Stereo Track to Mono”? When I tried this second option it creates two files. I can make one the right channel and one the left channel. Would that solve the problem?
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If you know, from the extreme zoom method that the left and right sides are out of step with each other, that can be fixed.

Split Stereo Track (but leave them left and right). Select the bottom track by clicking just above MUTE. Effect > Invert. Then Make Stereo Track (from the top track). That’s it. The stereo track is normal now.

You can zoom back in close to see the waves are going the same direction now, and even better don’t vanish any more.


Thank you for all your help. I just wanted to verify a couple things.

  1. In the attached photo is our theme music, which had no issues. I see small variations in the top and bottom stereo tracks. Is this what you are saying I should look for to make sure the audio will still be heard if someone is listening in mono ? I’m just thinking for future YouTube clips I grab, I want to be able to check and see if they will work fine without going through the process of fixing them first.

  2. If I do need to fix the track I:
    -Select Split Stereo Track
    -Select Invert for the bottom track
    -Select Make Stereo Track for the top track.
    And that’s all I have to do to fix the problem? And would it potentially cause any issues if I did it unnecessarily?

Thanks again!
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Is this what you are saying I should look for to make sure the audio will still be heard if someone is listening in mono ?

No. That’s perfectly normal in a stereo show. For example, in an orchestra, the violins will be predominantly on the left, less on the right. So during a violin passage, those two blue waves will be significantly different.

First you should be inspecting a loud passage rather than blue waves that are almost a straight line. I know what I’m looking for and I can’t tell from that illustration. They’re not tall enough.

In the case of a clip likely to vanish, all or most of the blue waves will be mirror images of each other. One goes up and the other goes down. Most observers would call that out of phase or “broken.”

And would it potentially cause any issues if I did it unnecessarily?

Nice try. That little dance, to drop into precise English for a second, reverses in-phase and out-of-phase. If it was broken before, that will fix it. If the clip was healthy, this will break it.

So it pays richly to know ahead of time what you have. Probably the easiest way is Tracks > Stereo Track to Mono. If the clip vanishes or drops significantly, it’s very probably broken. Edit > UNDO.

From 10,000 feet: The out of phase problem is pretty rare. It’s terrifically difficult to get a digital system to do it by accident and there are relatively few ways to get an analog system to do it. I’ll go out on a limb and say all your damaged clips are coming from the same Producer.

Run away.

If you’re using the clips by permission, you might drop them a message.


Ah, great! I will just test the clips by switching the stereo track to mono in the future.

I wish the problem were more rare. It’s happened on several of our podcast episodes when I have pulled show clips off of YouTube, from a variety of different YouTube users. We only use brief snippets of the TV shows we are talking about so it falls under fair use.

Perhaps it is because it is a low quality video on YouTube to begin with. But either way, from now on I will just test the clips by switching them to mono, and then go through the repair method you explained in your previous post if necessary.

Thanks for your help!

Could you give a link to one of the YouTube videos that had this problem. It could be useful for us to check if it is actually the video that has the problem, because if it’s not, then it must be something that you are doing.

Or better still, two videos.


Never mind. H R Pufnstuf 017 Jimmy Who is YouTube posted out of phase. It sounds funny when I listen (hole in the middle effect) and the blue waves are clearly out of phase when I download it with SoundFlower.

One Sabrina Adkins is responsible for that show and a number of others. I suspect strongly just looking for that YouTube Producer would be a good guide for whether the show is damaged or not.

H R Pufnstuf 008 is damaged, too.

I wonder if she has contact information…

I wonder if I have a YouTube account.


H R Pufnstuf In 3D - The Horse With The Golden Throat
Producer KingGhidorah58

Is OK.

We watch a different show each week so it’s always a variety of different YouTube users I am pulling from. I don’t quite have the ear for listening if it is out of phase on the video so I’ll just have to check when I open the file in Audacity.

Thanks again for your help!