Not only does it shackle the user upside down in a vat of chilling water, it's also impossible to listen to music inside the thing. If the legendary escape artist were alive today, he could make use of special underwater earbuds. Better yet, he could outfit the entire torture cell with a stunning underwater sound system.
But of course you're no Harry Houdini, and you probably don't earn your living inside a theatrical drowning booth. Yet even outside the world of professional illusion, underwater sound system technology has its place. Characteristics and Analysis of Sonar Waveforms. Ray Trace Modelling of Sonar Propagation. Normal Mode Modelling of Sonar Propagation. Noise and Reverberation. Acoustic Transduction. Transducer Arrays.
Underwater acoustic localization of marine mammals and vehicles
For time delay estimation in digital sampling systems, the proposed method can overcome the limited sampling frequencies without increasing computation complexities. The authors declare that there are no conflicts of interest regarding the publication of this paper. National Center for Biotechnology Information , U. Journal List Sensors Basel v. Sensors Basel. Published online Mar Author information Article notes Copyright and License information Disclaimer. Received Dec 28; Accepted Mar 9. Abstract This paper proposes underwater acoustic time delay estimation based on the envelope differences of correlation functions EDCF , which mitigates the delay estimation errors introduced by the amplitude fluctuations of the correlation function envelopes in the traditional correlation methods CM.
Keywords: time delay estimation, envelope differences of correlation functions, correlation method, underwater acoustic localization. Introduction Time delay estimation has been a key issue in underwater acoustic localization, detection, and communications [ 1 , 2 ]. Time Delay Estimation Method Based on Envelope Difference of Correlation Function In the traditional correlation method, the additive noise is not ideal Gaussian white noise and the signal sampling period is not infinitely long in practical applications, so R s v l T s may not necessarily strictly zero.
Open in a separate window. Figure 1. Figure 2. Figure 3. Figure 4. Precise Time Delay Calculation If the time delay estimation based on correlation envelope differences is performed via digital samplings, zero-crossing points cannot be directly solved due to the sampling intervals. Figure 5. Schematic diagram of two-point linear approximate exact solution time delay.
Anti-Multichannel Channel Performance Analysis In shallow sea conditions, multipath channels have significant impacts on time delay estimation. Figure 6.
Underwater acoustic communication
Figure 7. Shows the error of multipath delay calculation at different distances. Experimental Data Analysis The performance of the time delay estimation algorithm proposed in this paper was evaluated through sea trials. Figure 8. Figure 9. The correlation function envelope in test data the main peak.
Figure The correlation envelope function difference result in test data.
The correlation envelope function difference result in test data the main peak. Table 1 Comparison of time delay estimation performance between the correlation method and the correlation function envelope difference method. Conclusions In this paper, an approach based on the differences of correlation function envelopes has been proposed to estimate the time delay, which can avoid the delay estimation errors caused by the peak amplitude fluctuations of the correlation function envelope and significantly improve the accuracy of the time delay estimation. Author Contributions G.
Conflicts of Interest The authors declare that there are no conflicts of interest regarding the publication of this paper. References 1.
Zhang L. Acta Electron. Bharathi B. Carter G. IEEE Trans. Speech Signal Process. Bell B. Separating multipaths by global optimization of a multidimensional matched filter. Knappp C. The generalized correlation method of estimation of time delay.
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