Acoustic intensity in the ear canal. Incident, reflected and emitted waves

The present report describes a new method to directly measure the acoustic intensity of incident and outgoing sound waves in the ear canal in response to continuous broadband stimuli. The method was applied in normal hearing adults to determine the frequency-dependent input impedance and power reflection coefficient of the ear. The reflection coefficient exhibited a minimum value of ∼0.3 near the primary resonant frequency of ∼2.5 kHz. Preliminary data further indicate that the reflection coefficient may change with stimulus wavefrom amplitude, temporal structure, and ear canal exit impedance - observations indicating nonlinearity of the acoustic input-output behavior of the ear. Results have implications regarding assessment of middle ear and cochlear physiology using noninvasive ear canal pressure measurements.