“Ultimately, they settled on approximately 3.2 kHz.” doesn’t really explain who made this decision, when, or why. All we get is “Long ago, when the phone netwo

“Ultimately, they settled on approximately 3.2 kHz.” doesn’t really explain who made this decision, when, or why. All we get is “Long ago, when the phone networks were still completely analog, when the first real phone networks were being built, the engineers that were designing them faced a decision.” Who were those engineers? What company? How did they test what would be adequate bandwidth?