Measuring otoacoustic emissions (OAEs) in the ear is used for objective auditory checks (e. g. in infants) by testing the function of the inner ear (cochlea). OAEs are active acoustic emissions of the ear which – in a direction opposite to that of perceived sound find their way into the auditory canal via the ossicles and the eardrum, and can be detected there by means of highly sensitive measuring microphones. Such OAEs can be detected in approx. 97 % of human subjects. The properties of the human ear canal, however, differ significantly from one person to another, so that for the measurement of OAEs, the sound pressure can be determined with limited accuracy only. PTB’s invention consists in a probe with an adjustable microphone placement and an alterable acoustic impedance, which can be varied, for example, using micromechanical or micropneumatic control devices. At first, the source impedance and the open-circuit sound pressure of the probe can be calculated from additional measurements performed outside of the ear canal. Further measurements using the probe in the ear canal enable, in a second step, the determination of the source impedance and open-circuit sound pressure characterizing the emission from the cochlea. This invention is dedicated to determining the auditory sensitivity of patients in a safe and accurate manner.
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