排序方式： 共有4条查询结果，搜索用时 125 毫秒
1
1.
A simple, straightforward derivation of three necessary conditions that define the region of validity for the near-field directivity function (beam pattern) of an aperture (array) is presented. The derivation of all three criteria is based on determining what conditions must be satisfied in order to obtain a valid Fresnel approximation of the time-independent free-space Green's function. Comparisons with other near-field conditions in the literature are made 相似文献
2.
A recursive ray acoustics (RRA) algorithm for three-dimensional speeds of sound is presented. The RRA algorithm is simple, fast, and accurate and uses arc length as the independent variable. In its present form, it can be used to compute the position, angles of propagation, travel time, and path length along a ray path. Preliminary results from computer simulation studies designed to test the algorithm's accuracy and capabilities are also presented 相似文献
3.
New three-dimensional ray-acoustics expressions for the amplitude, eikonal, and phase along a ray path are derived. These expressions clearly indicate the numerical calculations that must be performed in order to evaluate these functions. The ocean medium is characterized by a three-dimensional random index of refraction which is decomposed into deterministic random components 相似文献
4.
Sound-pressure level (SPL) calculations are made along individual ray paths for arbitrary, one-dimensional, depth-dependent speeds of sound using an enhanced version of the RRA (recursive ray acoustics) algorithm. The SPL calculations are valid (i.e., finite) at turning points and focal points and do not require the use of Airy functions. The SPL calculations include the effects of frequency-dependent volume attenuation and frequency-dependent attenuation due to surface and bottom reflections. The ocean surface and bottom are treated as boundaries between viscous fluid media. Although the ocean surface is modeled as a planar boundary, the bathymetry is an arbitrary function of horizontal range. Sound speed versus depth and bathymetric data are represented by orthogonal function expansions. Computer simulation results from preliminary test cases are presented 相似文献
1