Parametric model of young infants’ eardrum and ear canal impedances supporting immittance measurement results. Part II: Prediction of eardrum and ear canal impedances for frequent pathological middle ear conditions

In order to gain a better understanding of wideband acoustic immitance (WAI) measurements, in this second part of a two-part paper, the parametric electro-acoustic model of the ear canal and the middle ear of young infants proposed in the first part is extended. The extension allows predictions of the influence of the pathological middle ear conditions middle ear effusion and negative static air pressure difference between the middle ear and the ear canal. Comparisons of the acoustic input impedance of the ear predicted by the model with real ear measurements in young infants’ ears with middle ear effusion show that the effects due to the pathology can be predicted well. For the negative static air pressure, a modeling approach was proposed but could not be confirmed yet, due to a lack of available measurement data. Furthermore, comparisons between different middle ear states (healthy, middle ear effusion and static air pressure difference) predicted by the model showed characteristic differences in all relevant WAI measures. However, it is also shown that WAI measures requiring an estimate of the cross-sectional area at the measurement position, i.e., absorbance and reflectance, are highly sensitive to this estimate

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

Wideband acoustic immitance (WAI) measurements provide an objective means to detect pathological middle ear conditions. However, for ears of young infants, it is still difficult to make clear statements about the middle ear status based on WAI measurements. In order to gain a better understanding of WAI data obtained in young infants’ ears, a parametric electro-acoustic model of the ear canal and the middle ear of young infants is proposed. In this first part of the two-part paper, the development of the model for the healthy ear is presented. Based on an existing model for adult ears, the presented model is adapted to young infants’ ears, uses parameters suited to represent physiological properties, and uses a smaller number of parameters in order to reduce model complexity. A comparison of the acoustic input impedance of the ear predicted by the model with real ear measurements in young infants’ ears showed a good agreement in the main characteristics. Model predictions show that the medium frequency range (about 1–3 kHz) of the acoustic input impedance of the ear is dominated by the properties of the eardrum and the middle ear, indicating that pathological middle ear conditions can preferably be detected in this frequency range