Left/Right - Good when editing, Bad on output

MacOS Sierra - 10.12.6
Audacity - 2.0.5

I am currently working on a project that has specific sounds on the left/right channel. When I’m working on the aup project file and playback, it pans left/right correctly when it is supposed to.

However, when I export (have tried several different formats), the sounds that should be in the left channel only, also come across in the right channel. Not sure where to start troubleshooting this?


Try importing the file that you exported, back into Audacity. If it plays OK in Audacity, then the problem is with the playback system. If it does not play correctly in Audacity (but the original project does), then the problem is with the exported file.

Some computer sound-cards apply a “virtual surround-sound” effect : that mixes the left & right channels a little, (aka crossover). If that is the cause, the “virtual surround-sound” can be turned-off, (but I don’t know where that is on a Mac).

Ok, after much more troubleshooting, here are some updates: 1

  1. The audio from the track seeps through to the right track, both in the aup file and output. It’s more pronounced in the output which is why I couldn’t at first notice it on the aup file.
  2. I have tested multiple outputs (mp3, ac3) and also tested multiple speakers / players to ensure it’s not my mac (iphone, mac speakers, mac via headphone jack).

Here is an image https://imgur.com/a/LAznC where, to troubleshoot, Track one is Left and pan is set to left. Track to is right and panned to right. During the visible spot here, there should only be audio on the left channel. Right now, there is audio on the left channel And audio (although super quiet) on the right channel. It’s super-quiet (but definitely there) in the aup file and much louder when I export it.

I hope this is making sense because it’s driving me nuts :slight_smile:

Drag-select a portion of the “dead” track and Analyze > Contrast > Measure Selection. When I do that, I get background noise in the -85dB range. Practically zero. That’s what you should get. I expect it to work.

Macs don’t naturally apply effects and filters to playback in real time, but an application could be “helping you.”

This is a Left-Right sound test I shot a while ago. It’s 39 seconds.


It’s clean.


When you push the sliders to the left and right extremes, does the little action graphic say “100%?”

The two export file types you gave as illustration are both compressed filetypes and “mess with the sound.” Does it do that if you Export WAV (Microsoft).


Fascinating! This is super-helpful - thank-you!

  • The pan left/right is at 100%
  • It occurs with a WAV file as well
  • It does it to the sample you provided as well (on my mac, played either via VLC or Audacity) - I.E. I hear your voice (at a much less volume level) in my right ear when you are speaking on the left and vice versa.
  • It does a similar thing while playing it on my iPhone with Quicktime (i.e. nothing to do with my computer)

However, it does NOT do it (the sound is 100% clean) when I airplay it to my amp/speakers. That is very bizarre.

Thank-you for the sample - help me to realize it wasn’t me. I have spent hours on this project trying to figure this out :slight_smile:

help me to realize it wasn’t me.

That’s why I recorded that piece. Basic troubleshooting. Split the system in half and see which half breaks.

The original reason for that test clip was to test for accidental wires reversed in sound systems. The fourth segment, “out of phase” should sound odd or like it’s coming from behind you. If the wrong segment does that, you got problems. The fourth segment should vanish in mono-mix systems.


Are all the errors happening with one set of earphones? Beats by Dr Dru, or Dr Dre. One of those doctors.

Do you still have the earbuds you got with your iPhone/iPod?


OK, probably not that one.



Are all the errors happening with one set of earphones? Beats by Dr Dru, or Dr Dre. One of those doctors.

Do you still have the earbuds you got with your iPhone/iPod?

it was three different headphones I used (all with the same result). I will see if I can track down the original Apple ones… Thanks again for all of your help.

I’m with you. You have impossible symptoms. I should go back and read through that again. The only way you can get a clean playback is use non-wired speakers?

Nowhere did anybody write you can’t have two problems.

There is no condition a good engineer can’t make worse.


it was three different headphones

You should start getting this stuff down to model numbers. All three made by the same company?


So I tracked down my original headphones and they work fine. Sigh. The headphones I were using were fairly high end so I didn’t even think to try the original headphones. Thanks again for leading me through some basic troubleshooting :slight_smile:

Were you using a jack adaptor with the high end headphones?

I used a variety of two/three stripe jacks initially to try to figure it out - all of which had issues. In the end, I’m fairly certain there may be a laptop connector issue as wireless is fine (airplay) and the person I sent the file to file was able to enjoy it correctly. Phew. :slight_smile:

Connector / adaptor are likely causes.