Ear-based tinnitus likely explains The Hum, new study suggests

A German study of 28 listeners found The Hum is unlikely to be caused by external low-frequency noise sources. Most participants did not have exceptional low-frequency hearing, and otoacoustic emissions could not account for the sound. The leading explanation is low-frequency tinnitus or heightened sensitivity to low-frequency hearing in some individuals, with more research needed to fully understand how the auditory system processes low-frequency sound and infrasound.