Blog
https://faculty.ksu.edu.sa/sites/default/files/Speech_Audiometry.pdf
https://www.steeneken.nl/wp-content/uploads/2014/04/Basics-STI_2014-V1.pdf
While reading Steeneken above, I had to draw it out just to make sense of the little nuance I could capture.
These articles have to do with Audio Competition.