This trick is interesting to me as someone who mixes records. I (and mixers in general) have a lot of different tricks for making mono audio objects in the mix feel stereo or have a sense of width or depth.
Examples include:
1. Delaying the left or right channel by a few ms (Haas effect).
2. De-tuning one of the channels by a few cents
3. Boosting an EQ band on one channel, with a complimentary cut on the opposite channel.
...and many more.
These are usually very subtle changes that our stereoscopic ears have no problem detecting.
In any case, when we need to do some forensic searching for possible differences between two near-identical channels we'll invert the polarity on one channel and then sum them. The resulting delta sticks out like a sore thumb and highlights even then tiniest differences between the files.
So it's fascinating to discover that we can easily do something similar with our eyes to find the differences.
Examples include:
1. Delaying the left or right channel by a few ms (Haas effect).
2. De-tuning one of the channels by a few cents
3. Boosting an EQ band on one channel, with a complimentary cut on the opposite channel.
...and many more.
These are usually very subtle changes that our stereoscopic ears have no problem detecting.
In any case, when we need to do some forensic searching for possible differences between two near-identical channels we'll invert the polarity on one channel and then sum them. The resulting delta sticks out like a sore thumb and highlights even then tiniest differences between the files.
So it's fascinating to discover that we can easily do something similar with our eyes to find the differences.