As already mentioned above, this denotes a certain note on which the digestive system must perform an act of defecation.
In theory, a sound that is low enough in pitch should produce a vibration that shakes all the organs responsible for digestion and cause them to upset. Personally, I got to know this term playing a fairly well-known game based on the animated series South Park, one of the characters of which had the ability to "demoralize" the enemy due to this "brown note". Although this is just a fantasy of the developers, the idea itself could not come to their minds out of the blue. In Mythbusters it was denied and, unfortunately (or fortunately), denied. However, my personal experience tells me otherwise. I came across strong bass at some concerts that I had the opportunity to attend. In such cases, I often felt discomfort, which indicates the partial veracity of possible tales or stories associated with this topic.
I would say that everything depends on the organism itself, to which the low sound is directed, in particular on its digestion. You can experience and write about your impressions, but be careful if you are afraid of ruining your reputation by doing so.
I'm not sure what I say for everyone, but when listening to the musical group "Caspian Cargo" I really want to go to the toilet. This is probably the "Brown Note". Put in ha!
The term "brown note" refers to certain frequencies of sound at which a person experiences stomach upset. However, this has not been scientifically proven.
In "Mythbusters" (Season 3 Episode 25), sound equipment experts conducted an experiment with different sound frequencies, as a result of which the subject did not show any symptoms of feces.