The Zwislocki Acoustic Bridge (mechanical) and the Madsen Z070 Electroacoustic Bridge were compared in 11 normal hearing subjects. Both compliance and absolute impedance values at the eardrum derived with each instrument were correlated with each other and themselves on measurements repeated at three weekly intervals. Test-retest reliability is shown to be extremely high for each instrument and the correlation between instruments is similarly high. It is stressed, however, that these findings relate only to a normal population where the resistance component of impedance is a relatively stable factor that contributes minimally to total impedance measured at the eardrum.
Feldman AS, Djupesland G, Grimes CT. A Comparison of Impedance Measurements: With Mechanical and Electroacoustic Impedance Measuring Devices. Arch Otolaryngol. 1971;93(4):416–418. doi:10.1001/archotol.1971.00770060608011
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