A Finite Element Approach to Evaluate the Validity of Real-Ear Measurements as an Auditory Reference in Occluded Human Ears
* Presenting author
For audiological applications, real-ear measurements of the sound pressure at a single point in front of the eardrum are often used as reference, e.g. for hearing aid fitting.After sound is guided through the ear canal, acoustic energy is transduced to mechanical movement in the middle ear via the tympanic membrane. Due to the movement of the eardrum, the sound field in its direct vicinity might be strongly inhomogeneous. Additionally, standing wave patterns due to reflections at both ends of the canal occur. Hence, a well-known consequence is that the positioning of the microphone may have a significant impact on the measurement result. In addition, the characteristic of the sound field depends on the setup, e.g. with and without hearing aid. Thus, the dependency between the sound pressure at the reference point and the movement of the tympanic membrane can be different. In this work, this effect is analyzed with a simplified 3D finite element model. Therefore, requirements on an acoustical reference point are defined, and boundary conditions for closed hearing aid fitting are introduced. By analyzing the relation between sound pressure at varying reference points and mechanical displacement of the eardrum, the validity of single reference points is rated.