It is complicated to model the acoustic field in stratified ocean for airborne aircraft,due to high speed of the source and air-to-water sound transmission.To our knowledge,there are very few papers in the open litera...It is complicated to model the acoustic field in stratified ocean for airborne aircraft,due to high speed of the source and air-to-water sound transmission.To our knowledge,there are very few papers in the open literature dealing with this complicated problem;but,in our opinion,they all require great amount of computation.We now propose a different method that requires much less computation.We improve the wavenumber integration method to model the received temporal signal for a moving source in stratified ocean and sum up in a concise form the core of our paper as follows:(A) Eq.(11) can be calculated by means of fast Chirp Z transform and the signals at all N time points are generated simultaneously;(B) direct numerical evaluation of the wavenumber integral in Eq.(4) produces large numerical errors;so it is necessary to shift the integration slightly below the real axis;(C) we compare the computation cost of direct calculation method with that of our fast calculation method;from the results presented in table 1,we can see that the fast calculation method consumes much less computation time,particularly for long duration signals;(D) for an airborne rapidly moving source,we compute the Doppler-shifted signals in shallow water and analyze their short-time Fourier transform;from Fig.1b,we can see that the received signals have multiple frequency components for a tonal source due to source motion and that each component corresponds to an arrival path.展开更多
文摘It is complicated to model the acoustic field in stratified ocean for airborne aircraft,due to high speed of the source and air-to-water sound transmission.To our knowledge,there are very few papers in the open literature dealing with this complicated problem;but,in our opinion,they all require great amount of computation.We now propose a different method that requires much less computation.We improve the wavenumber integration method to model the received temporal signal for a moving source in stratified ocean and sum up in a concise form the core of our paper as follows:(A) Eq.(11) can be calculated by means of fast Chirp Z transform and the signals at all N time points are generated simultaneously;(B) direct numerical evaluation of the wavenumber integral in Eq.(4) produces large numerical errors;so it is necessary to shift the integration slightly below the real axis;(C) we compare the computation cost of direct calculation method with that of our fast calculation method;from the results presented in table 1,we can see that the fast calculation method consumes much less computation time,particularly for long duration signals;(D) for an airborne rapidly moving source,we compute the Doppler-shifted signals in shallow water and analyze their short-time Fourier transform;from Fig.1b,we can see that the received signals have multiple frequency components for a tonal source due to source motion and that each component corresponds to an arrival path.
