The Effect of High Altitude on the Threshold of Hearing

The threshold of hearing has been measured in a decompression chamber at ambient pressUres corresponding to altitudes of 35,000 feet and sea level. After the data have been corrected for the change of cushion seal and the change in response of the earphone unit with change in pressure, the results show that the shift in the average threshold of hearing for fifteen ears is within ±2.5 db of sound pressure level when the density of the air in the outer and middle ear is decreased to about one‐fourth that at sea level.