Methodology of Designing an Occluded Ear Simulator

Several artificial ears have been developed over the last century, but to our knowledge, the design methodology has never been documented. In a Brüel & Kjær document (1976), the significance of parameters such as the acoustic transfer impedance and the acoustic impedance of the sound source are discussed, but details of how to handle these parameters in the design are not given. This paper therefore presents a model of a sound source coupled to the ear canal in order to illustrate the influence of these key parameters on the overall ear simulator design, leading to a systematic design methodology. Using this technique and reported typical variations in the geometry of adult ear canals, a calculation by a Monte Carlo simulation is described. This has been used to estimate the typical errors that can occur in audiological screening, when using for example, an audiometer calibrated by a standard ear simulator. Finally, a methodology of designing an occluded ear simulator resulting from this study is provided, in view of designing a new family of occluded ear simulators developed for target age groups, from neonates to adults. This work is part of the EMRP EARS Project.