By Finn B. Jensen, William A. Kuperman, Michael B. Porter, Henrik Schmidt
Since the mid-1970s, the pc has performed an more and more pivotal function within the box of ocean acoustics. quicker and cheaper than genuine ocean experiments, and able to accommodating the whole complexity of the acoustic challenge, numerical types at the moment are average learn instruments in ocean laboratories.
The growth made in computational ocean acoustics over the past thirty years is summed up during this authoritative and innovatively illustrated new textual content. Written through many of the field's pioneers, all Fellows of the Acoustical Society of the USA, Computational Ocean Acoustics offers the newest numerical strategies for fixing the wave equation in heterogeneous fluid–solid media. The authors talk about numerous computational schemes intimately, emphasizing the significance of theoretical foundations that lead on to numerical implementations for genuine ocean environments. To extra make clear the presentation, the elemental propagation positive aspects of the concepts are illustrated in color.
Computational Ocean Acoustics conveys the state of the art of numerical modeling strategies for graduate and undergraduate scholars of acoustics, geology and geophysics, utilized arithmetic, and ocean engineering. it's also a necessary addition to the libraries of ocean study associations that use propagation models.
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Additional info for Computational Ocean Acoustics
Optimum frequency is a general feature of ducted propagation in the ocean. It occurs as a result of competing propagation and attenuation mechanisms at high and low frequencies. In the high-frequency regime, we have increasing volume 32 1 Fundamentals of Ocean Acoustics and scattering loss with increasing frequency (see Sects. 7). At lower frequencies the situation is more complicated. With increasing wavelength the efficiency of the duct to confine sound decreases (the cutoff phenomenon). Hence, propagation and attenuation mechanisms outside the duct (in the seabed) become important.
1), thus transforming the duct into a non-guiding isospeed surface layer. Finally, it should be pointed out that the ray picture in Fig. 13 is entirely misleading at low frequencies. In fact, the surface duct ceases to trap energy when the acoustic wavelength becomes too large. This wave-theory cutoff phenomenon, common to all types of ducted propagation, shall be dealt with in detail in Chaps. 2 and 5 when discussing propagation in terms of normal modes. Here it suffices to give an approximate formula for the cutoff frequency below which no energy can propagate in the surface duct.
P1 =p2 / where it is understood that the reference originates from the intensity of a plane wave of pressure equal to 1 Pa. The average intensity I of a plane wave with rms pressure p in a medium of density and sound speed c is I D p 2 =Z, where Z D c is called the acoustic impedance. , 0 dB re 1 Pa). 2 Spectrum Level The above discussion has direct application to both single frequency and continuous wave (CW) signals. However, very often we are concerned with broadband signals or noise. In this case, we must refer the acoustic intensity to a bandwidth and very often the reference bandwidth is 1 hertz (Hz).