Since the early 1990s, residents of Taos have reported a persistent low-frequency humming sound, often described as a faint engine idling just beyond hearing range. In 1993, Congress even commissioned an official study, but scientists could not pinpoint a source—ruling out industrial noise, seismic activity, and radio transmissions. Only a small percentage of people can hear it, adding to the mystery and leading some to speculate about UFOs, secret military projects, or psychological phenomena. The “Taos Hum” remains one of America’s most famous unexplained acoustic mysteries.