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Autonomous underwater gliders (AUGs) are autonomous vehicles that propel themselves by changing their buoyancy through the ocean. For ocean observations, AUGs have unparalleled advantages that can operate in all weather conditions, for long time periods, and in remote locations. However, AUGs have limitations such as instrument and flow noise, which are undesired. To obtain the valid information from...
Multistatic sonar has the characteristics of traditional passive and active sonar, including good concealment performance, strong anti-interference ability, far-distance reaction, high positioning accuracy, the advantages of easy-to-optimization design, etc. Multistatic sonar will be the important direction for future development of active sonar. About the scattering characteristics of multistatic...
Temperature has a considerable influence on the shallow water. Due to important economic value and relation to human activity, the on-line and real-time water temperature monitoring is of great scientific and practical significance. This paper has performed an experiment of a high frequency acoustic temperature measurement. Reciprocal sound transmission and the signal cross-correlation method were...
Explosive charges are widely used in underwater acoustics experiments because it has wide bandwidth and high source level. the received signals are the shock wave and followed by a series of bubble pulses, which seriously affect the observation and applications of the signal. But for the shallow water waveguides, the bubble pulses could be seen as anther “signal”. In this paper, we treat the first...
This paper characterizes sediment geoacoustic properties using single beam sonar echoes collected from a sea trial conducted in 2010. The characteristic parameters of a sediment, e.g., mean grain size are estimated by matching the envelops of collected echoes and predicted replicas by a high-frequency backscattered model. The envelopes of real data were first averaged over a certain number of pins...
The vocal mechanism and structure of ship radiated noise and marine biological noise are analyzed, and the differences of short-term inter-frame spectral similarity between the two kinds of noise are compared. On the basis of this, Pearson correlation coefficient variance of the spectral trend of the adjacent two frames in the short term of the framing signal is used as the recognition feature. A...
Underwater acoustic source localization has attracted wide interests, and the source depth estimation is more difficult than that of source range and bearing. The performance of Matched Field Processing (MFP) degrades greatly under environment parameter mismatches, which makes it limited in practice. Varieties of robust methods have been proposed to relieve the mismatch problems. T. C. Yang proposed...
The noise spatial correlation coefficient between two array elements deployed vertically in real deep ocean environment is not consistent with that in isotropic ambient noise field because of surface-distributed wind driven noise sources. Therefore, it is necessary to analyze the performance of vertical line array spatial gain properly. A method for modeling wind-driven ambient noise field is described...
How a grain ahead affecting a dolphin's transmitting performance is examined. A finite element approach was applied to numerically simulate the acoustic field around a dolphin with a small grain ahead of it. Acoustic intensity distribution, beam pattern, angle of strong beam and 3dB beam width are compared to investigate the differences caused by the small grain ahead of the dolphin. Although the...
The speed of the target can be estimated by the sound pressure cross-correlation of the line spectrum of the moving target at different time intervals. However, a slight deviation of the line spectrum has a significant influence on the estimated result. In this paper this phenomenon is analyzed from the theory, then the speed of the target is estimated when the line spectrum is biased. Experimental...
Based on the characteristics of short pulse signals in the marine animals sound and the characteristics of the high temporal resolution of the wavelet transform, this paper proposed a new strategy of Constant False Alarm Rate(CFAR) pulse detection based on continuous wavelet transform(CWT). The CFAR pulse detection was carried out on each scale of the results of time frequency analysis of CWT. Then...
Effects of anthropogenic noise on marine fish have drawn increasing attention. In order to explore the effects of underwater noise on false kelpfish (Sebasticus marmoratus), the acoustic stimulus experiments were carried in a tank with three types of noise sources and analyzed with behavioral method. The results showed that when peak and effective sound pressure levels (SPLpeak, SPLrms) were above...
Marine mammal tonal vocalizations are studied to help marine biologists get a better knowledge of their behavioral context. The vocalizations are often analyzed by characterization of the frequency contours. An automated frequency contour extraction method extended by image-based technique is proposed. The spectrogram is first de-noised and then two binary images are derived with a low threshold and...
In this paper, matched-field localization with a single vector hydrophone is researched. In condition of ideal waveguide, the sound pressure field and vertical velocity were analyzed theoretically. The relationship between acoustic pressure field and vector field achieved that a vector hydrophone can be equivalent to vertical two element array with a certain vertical aperture. The depth of vector...
This paper aims to detect narrowband signal embedded in the noise background using a single acoustic vector hydrophone. In the isotropic noise field, processing on acoustic energy flow is the maximum likelihood ratio detector. Adopting ideas of the average power spectrum, we propose a narrowband detector based on the cross spectrum between acoustic pressure and acoustic particle velocity. Firstly,...
When the inertial navigation system is positioning underwater vehicle such as the AUV, it can be achieved without any outside information, and be real-time and autonomy for AUV navigation. It can navigate the AUV real-timely and independently without the help of any outside information. However, the positioning accuracy will reduce with the increasing cumulative error when the inertial navigation...
A model-independent method of the range localization for a moving source using a single receiver is derived. The Demon (detection of envelope and modulation on noise) spectrum demodulated from the broadband noise of the vessel is obtained by the absolute low pass demodulation technology. A relationship between the range interval and the difference between the acoustic field at two different ranges...
The classification of different odontocetes using écholocation clicks plays a significant role in tracking and detecting animals for research and protection purposes. Echolocation clicks were detected by an automatic method based on the Teager-Kaiser Energy Operator (TKEO). Then, these clicks were represented by their FFT magnitude spectrum. To reduce the influence of high similar clicks among species,...
Linear prediction is a commonly used approach to preprocess microphone signals for estimation of time delays from an acoustic source to different microphones. A typical linear prediction algorithm employs the least squares criterion to solve an optimization problem. This criterion, however, is not optimal for non-Gaussian distributed speech signals. In this paper, we propose a sparse preprocessing...
Bottlenose dolphins (Tursiops truncatus) are gregarious marine mammals. They use powerful sonar system to communicate underwater and transmit click signals for echolocation. The impact of underwater noise on marine mammals has become major concern. The knowledge regarding the influence of marine mammals on underwater acoustic instruments were unknown. Since the frequency of bottlenose dolphins' click...
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