The tone was discovered in approximately 1957,[9] by Joe Engressia, a blind seven-year-old boy. Engressia had perfect pitch, and discovered that whistling the fourth E above middle C (a frequency of 2637.02 Hz) would stop a dialed phone recording. Unaware of what he had done, Engressia called the phone company and asked why the recordings had stopped.[10]
Because @sanitation@lemmy.today was unable to properly add sources, I helped them out by looking for something on Wikipedia:
The tone was discovered in approximately 1957,[9] by Joe Engressia, a blind seven-year-old boy. Engressia had perfect pitch, and discovered that whistling the fourth E above middle C (a frequency of 2637.02 Hz) would stop a dialed phone recording. Unaware of what he had done, Engressia called the phone company and asked why the recordings had stopped.[10]