A deep transfer learning (DTL) method is proposed for the direction of arrival (DOA) estimation using a single-vector sensor. The method involves training of a convolutional neural network (CNN) with synthetic data in source domain and then adapting the source domain to target domain with available at-sea data. The CNN is fed with the cross-spectrum of acoustical pressure and particle velocity during the training process to learn DOAs of a moving surface ship. For domain adaptation, first convolutional layers of the pre-trained CNN are copied to a target CNN, and the remaining layers of the target CNN are randomly initialized and trained on at-sea data. Numerical tests and real data results suggest that the DTL yields more reliable DOA estimates than a conventional CNN, especially with interfering sources.
The vestibular and cochlear aqueducts serve as additional sound transmission paths and produce different degrees of volume velocity shunt flow in cochlear sound transmission. To investigate its effect on forward and reverse stimulations, a lumped-parameter model of the human ear, which incorporates the third windows, was developed. The model combines a transmission-line ear-canal model, a middle-ear model, and an inner-ear model, which were developed previously by different investigators. The model is verified by comparison with experiments. The intracochlear differential-pressure transfer functions, which reflect the input force to the organ of Corti, were calculated. The results show that middle-ear gain for forward sound transmission is greater than the gain for reverse sound transmission. Changes in the cochlear aqueduct impedance have little effect on forward and reverse stimulations. The vestibular aqueduct has little effect on forward stimulation, but increasing its impedance causes deterioration on reverse stimulation below 300 Hz. Decreasing its impedance increases the excitation effect during reverse stimulation over the entire frequency, especially below 1000 Hz. Moreover, compared with the case without the third windows, the presence of the third windows has little effect on forward stimulation. Whereas, it boosts the reverse stimulation's performance below 300 Hz.
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