Short answers, pulled from the story.
White noise is a random signal that has equal intensity at every frequency, producing a constant power spectral density. It functions as a statistical model rather than any single specific signal, and the term appears across physics, acoustical engineering, telecommunications, and statistical forecasting.
White noise takes its name from white light, even though light that looks white typically does not have a flat power spectral density across the visible band. The term borrows the idea of even distribution, applied to frequencies instead of colors of light.
Traveling salesman Jim Buckwalter built the Marpac Sleep-Mate in 1962, the first white noise machine made for domestic use. It offered a manufactured alternative to tuning an AM radio to an unused frequency for static.
The effects are mixed. A 2007 study found background white noise improved cognitive functioning for secondary students with ADHD while lowering performance for students without the condition, and a separate experiment on sixty-six healthy participants found white noise gave a slight boost to learning and recognition memory.
No. Gaussianity describes the probability distribution of a signal's amplitude, while whiteness describes how a signal's power is distributed across time or frequency, and neither property implies the other.
White noise has equal intensity across every frequency, while pink noise has equal energy in each octave instead. Because white noise carries too much high frequency content for loudspeaker testing, pink noise is used to test transducers such as loudspeakers and microphones instead.