A Classification of Environmental “Hums” and Low Frequency Tinnitus

Abstract

Two thousand people in the United Kingdom have complained of hearing a continuous hum, audible to themselves alone. Some of these “hummers” were given acoustic tests comprising hum-matching, normal and low-frequency audiometry, and a tinnitus versus real-airborne-noise distinguishing test. Results were compared with those from seventy-three control subjects (audiometry alone) and with fifty-five hospital out-patients known to have low-frequency tinnitus. It is shown that the frequency distributions of “hummers” hums and throbs correlate closely with those of patients' low-frequency tinnitus, although no causal link is established. A general classification of hum types is proposed and means for distinguishing them are described. Applied to 48 “hummers” these show that ten have low-frequency tinnitus and four are hearing a real airborne noise. The remaining, 4 cannot be classified, mainly because they did not take all the tests. It is not claimed that these figures apply to “hummers” in general since the 48 tested were not a true sample of the “hummer” population.