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

Abstract

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.

Keywords

• acoustic impedance
• admittance
• middle ear
• outer ear
• screening