Methods and reference data for middle ear transfer functions (original) (raw)

Human temporal bone specimens are used in experiments measuring the sound transfer of the middle ear, which is the standard method used in the development of active and passive middle ear implants. Statistical analyses of these experiments usually require that the TB samples are representative of the population of non-pathological middle ears. Specifically, this means that the specimens must be mechanically well-characterized. We present an in-depth statistical analysis of 478 data sets of middle ear transfer functions (METFs) from different laboratories. The data sets are preprocessed and various contributions to the variance of the data are evaluated. We then derive a statistical range as a reference against which individual METF measurements may be validated. The range is calculated as the two-sided 95% tolerance interval at audiological frequencies. In addition, the mean and 95% confidence interval of the mean are given as references for assessing the validity of a sample group. Finally, we provide a suggested procedure for measuring METFs using the methods described herein. Abbreviations AMEI Active middle ear implant ASTM American Society for Testing and Materials CI Confidence interval dBSPL Decibel sound pressure level dB SPLeq. DB SPL equivalent FFT Fast Fourier transform IQR Interquartile range LDV Laser Doppler vibrometer METF Middle ear transfer function OC Ossicular chain SFP Stapes footplate SFV Stapes footplate velocity SHV Stapes head velocity SNR Signal to noise ratio TB Temporal bone specimen TI Tolerance interval TM Tympanic membrane LDV angle of incidence relative to normal of the SFP Background. Experimental studies using human cadaveric temporal bone (TB) specimens are an important tool for the understanding of middle ear mechanics and the development of new surgical procedures, diagnostics, or devices for hearing rehabilitation. Transferring the insights gained by such studies into real-world applications, however, requires classifying the mechanical properties of the samples used in relation to the population. An important characteristic here is the sound transfer from the tympanic membrane (TM) through the ossicular chain (OC) into the inner ear, which for non-pathological human middle ears and sound pressures of