Short answers, pulled from the story.
Claude Shannon published a paper that introduced the concept of white noise in 1948. This publication established white noise as a statistical model rather than a specific physical sound.
The human ear perceives white noise within the audible frequency band ranging from 20 hertz to 20,000 hertz. This perception occurs as a hissing sound resembling the /h/ phoneme during sustained aspiration.
Jim Buckwalter built the Marpac Sleep-Mate starting in 1962. He was a traveling salesman who designed the device specifically for household use.
Pink noise differs by having equal energy per octave rather than per hertz. White noise maintains constant power spectral density over a relevant range while pink noise adjusts for octaves.
A small study published in 2007 found that background white noise improved cognitive functioning among secondary students diagnosed with attention deficit hyperactivity disorder. The same stimulation decreased performance levels for non-ADHD students participating in similar tasks.