Characterization and Clinical Trials of the Prototype Ear Simulator Designed for Neonates Hearing Assessment

This article aims to describe the characterization of the new prototype ear simulator for neonates and demonstrate its utility in clinical measurements. Experimental evaluations have been performed in order to demonstrate consistency with the theoretical model in acoustic transfer impedance. Temperature and atmospheric pressure dependency measurements have been applied for verification of the stability of the ear simulator in variable environmental conditions. Thus, the main objective of this study is to outline the benefits of the new ear simulator in audiometric measurements for neonates. Acoustic transfer impedance of the ear simulator has been determined and compared with the theoretical model, and its environmental dependence has been studied between 100 Hz and 10,000 Hz. A modified method usually applied for reciprocity calibration of microphones has been used in measurements. Comparison of the new ear simulator with the IEC 60318-4 ear simulator and a \(2\,\hbox {cm}^{3}\) coupler has been presented. The ear simulator has been used to calibrate acoustics stimuli from an audiometer (Interacoustics AD226 with Otometrics insert earphone) and two otoacoustic emission devices (Otodynamics Otoport and Interacoustics Titan). The consistency of experimental evaluations in acoustic transfer impedance with the theoretical model has been confirmed. In clinical trials, an audiometer and two otoacoustic emission devices were investigated and a smaller standard deviation of 1.0 dB, 0.8 dB and 0.7 dB at 1 kHz, 2 kHz and 4 kHz, respectively, has been achieved compared to the old \(2\,\hbox {cm}^{3}\) coupler which has a 1.5 dB, 1.8 dB and 1.9 dB standard deviations at same frequencies. Average differences and standard deviations between the two couplers (IEC 60318-4 and the universal ear simulator) are \(11.4 \pm 0.3\,\hbox {dB}\) at 1 kHz, \(11.0 \pm 0.1\,\hbox {dB}\) at 2 kHz and \(13.3 \pm 0.2\,\hbox {dB}\) at 4 kHz. These differences represent the error incurred by using an adult ear simulator for neonates applications. The new universal ear simulator designed especially for hearing assessments of neonates has been characterized and used in clinical trials. The consistency between theoretical model and experimental measurements has been approved. Clinical trials showed that a more accurate calibration of OAE and audiometers for neonates would be possible. However, further applications for different age groups and broader clinical trials should be planned. Intercomparisons between different laboratories and clinics can maintain the comparability of hearing measurements and higher impact.