Abstract
The application of the sound wave which propagates through long range in the ocean is studied to monitor global warming. Recently, parabolic equation method (PE method) is often used as a sound propagation simulation technique. The PE method can calculate the sound field in high accuracy when the propagation range is short and the frequency is low. However, the error grows in a usual computational method when the propagation range becomes mega-range. Especially, the phase error in the time domain was not examined. The solution of PE method is a product of envelope function and Hankel function. The influence of Hankel function becomes big in the time domain because the received pulse consists of a lot of frequencies. This is a cause of the error of the pulse propagation time. In this paper, we theoretically outlined the difference between the phase error in the frequency domain and the phase error in the time domain. Moreover, the phase error in the time domain was simulated by selecting the sound speed in the envelope function and in the Hankel function. As a result, we show the importance of making the sound speed in the envelope function and in the Hankel function the same.
