Fluid-Structure Finite-Element Modelling and Clinical Measurement of the Wideband Acoustic Input Admittance of the Newborn Ear Canal and Middle Ear

Abstract

The anatomical differences between the newborn ear and the adult one result in different input admittance responses in newborns than those in adults. Taking into account fluid-structure interactions, we have developed a finite-element model to investigate the wideband admittance responses of the ear canal and middle ear in newborns for frequencies up to 10 kHz. We have also performed admittance measurements on a group of 23 infants with ages between 14 and 28 days, for frequencies from 250 to 8000 Hz with 1/12-octave resolution. Sensitivity analyses of the model were performed to investigate the contributions of the ear canal and middle ear to the overall admittance responses, as well as the effects of the material parameters, measurement location and geometrical variability. The model was validated by comparison with our new data and with data from the literature. The model provides a quantitative understanding of the canal and middle-ear resonances around 500 and 1800 Hz, respectively, and also predicts the effects of the first resonance mode of the middle-ear cavity (around 6 kHz) as well as the first and second standing-wave modes in the ear canal (around 7.2 and 9.6 kHz, respectively), which may explain features seen in our high-frequency-resolution clinical measurements.

Parametric model of young infants’ eardrum and ear canal impedances supporting immittance measurement results. Part I: Development of the model

“…At these frequencies Z ec transitions from dominance by Z D to dominance by the ear canal geometry. Compared to the measurements, the prediction of the present study tends to the maximum values measured and the prediction according to [46] tends to the lower values measured, however both predictions are within the range of measurements at frequencies between 2.4 kHz and 4 kHz. In the model according to [46], a resonance at about 6 kHz and a local minimum at 7 kHz can be seen which are not predicted with the model of the present study.…”

“…Compared to the measurements, the prediction of the present study tends to the maximum values measured and the prediction according to [46] tends to the lower values measured, however both predictions are within the range of measurements at frequencies between 2.4 kHz and 4 kHz. In the model according to [46], a resonance at about 6 kHz and a local minimum at 7 kHz can be seen which are not predicted with the model of the present study. In [46] it was explained that the resonance is caused by the first mode of the middle ear cavity and the minimum is caused by the first standing wave mode in the ear canal.…”

“…Finally, a model with material properties adjusted to match some clinical data was proposed. A refined version of the model, in which the frequency range was extended up to 10 kHz, was proposed in [46]. Compared to the model of the present study, their first version model results in similar predictions, see Figure 15.…”

A lumped-element model of the chinchilla middle ear

“…7(d)]. However, there are cochlear structures with effects not included in our model that may contribute to the cochlear load on sound transmission, in particular, the helicotrema, which is thought to affect the cochlear input impedance at low frequencies (Dallos, 1970;Lynch et al, 1982;Motallebzadeh et al, 2017b). Dallos (1970) attributed variations in the frequency dependence of the cochlear microphonic in chinchillas that occurred at frequencies below 0.3 kHz to the helicotrema.…”

Mechanical Properties of Baboon Tympanic Membrane from Young to Adult

“…Properties of the infants and young children's TMs are not well studied due to the scarcity of temporal bones from young children. These data, however, are important for understanding how middle ear diseases, such as otitis media, affect the hearing of the pediatric population (Qi et al 2008;Wang et al 2016;Motallebzadeh et al 2017b;Motallebzadeh et al 2017a).…”