What is the difference between stereo tracks called and is there a way I can hear only that difference?

When you record a stereo track from a dual condenser microphone there are very subtle differences between the stereo tracks. It may be Interference or slight differences between the mics, but I am wanting to hear what is there and see what it sounds like. How can I get Audacity set up so that it filters the tracks out, compares the differences between the tracks and then allows me to hear what is there? I am trying to hear a somewhat encoded message and decipher it. Someone has used a weird recording method to send a message in the Offset between the stereo tracks and I can vaguely hear talking between the channels when i play it back, I can see the changes in the DC Offset of the tracks is different, but the main tracks are too loud. What filter or setting can I use to be able to hear it better? This is wild almost like Backmasking in the records of the 50’s and 70’s but I guess a more modern way of doing it… How do I decode it with Audacity? I know sounds weird… Thought maybe some of you would be more expert at this than I am while I have been using Audacity for various things for years… This one is a stumper for me.

So what you can do is to use the Invert efect to “subtract” one channel from the other.

To do this:

  1. Click on the drop-down arrow in the Track Control Panel and select “Split Stereo To Mono”: https://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html#:~:text=Choose%20Split%20Stereo%20to%20Mono,lower%20track%20to%2070%25%20right.
  2. Select either track.
  3. Effect > Invert
  4. Tracks > Mix > Mix and Render

It’s called “side” … https://en.wikipedia.org/wiki/Microphone_practice#M/S_technique:_Mid/Side_stereophony


Alternatively it’s EVP (pareidolia) … https://en.wikipedia.org/wiki/Electronic_voice_phenomenon#Natural_explanations

The [u]Vocal Reduction and Isolation[/u] can also do it. Just choose the Remove Center option.

Someone has used a weird recording method to send a message in the Offset between the stereo tracks and I can vaguely hear talking between the channels when i play it back

You can’t get that from a stereo microphone but If the “message” is electronically/digitally inverted in one channel it will completely subtract-out when summed to mono.

You’ll still hear it in stereo because the soundwaves don’t completely cancel in the air. It makes a weird “spacey” effect and some people do it to make a stereo “widening” effect, but then the vocals (or whatever) get canceled on a mono phone-speaker. (Out-of-phase bass does get almost completely canceled in the air.) With headphones the left & right never mix so inverting one channel has no effect.


…You can make a “subliminal message” by mixing the message at -20 or -30dB with music or white noise. When you listen, the message is masked by the music/noise. But if you have exact copy of the music/noise without the message, you can invert and mix it with the other file and the noise/music will be completely removed, leaving the low-level message which you can boost to hear clearly. That could be done with two separate files, or you could make a “stereo” file where the channels are identical except for one channel having the low-level secret message mixed-in.