Standing‐wave pressure ratio in the human ear canal

The presence of an air column of uncertain size and shape in front of the eardrum makes it difficult to perform reliable measurements of eardrum impedance at frequencies greater than 2 kHz; the standing‐wave ratio, however, is relatively insensitive to irregularities in canal geometry and so provides a better characterization of the eardrum at these frequencies. The standing wave patterns occurring between 4 and 10 kHz in the human ear canal have recently been surveyed in a group of 13 normal ears. These data indicate substantially higher values of standing wave ratio (between 18 and 25 dB at 8 kHz) than previously reported (typically 13 dB at 8 kHz). The resulting smaller values of eardrum absorption coefficient (between 20% and 40%) are more consistent with the known properties of the human eardrum (mass, size, vibrational patterns, etc.). These results are an important step towards understanding the mechanics of the human eardrum and middle ear.