To the Editor.—The ongoing investigation of inversion as exercise or therapy1 has raised a new concern in my practice. Tinnitus was reported to me by a user of an inversion device, and a patient who is a musician asked if inversion would damage her hearing. Answers were not readily available from the literature, and E. Charles Kunkle, MD (written communication, 1962) suggested there were no substantial audiometric changes in the 50° head-down tilt.
To study this further, I selected 20 healthy college football players and subjected each to a ten-minute inversion, measuring various factors (other findings to be reported elsewhere). Pure-tone binaural air conduction testing was performed evaluating frequencies 250 through 8,000 Hz, using an appropriately calibrated audiometer. Transducer earphones were used, mounted in acoustically shielded audiocups. Background noise level at the subject's ear averaged 55 dB (mostly low-frequency noise well filtered by earphones). Baseline audiogram was done