On the synthesis of acoustic sources with controllable near fields

Abstract

In this paper we present a strategy for the the synthesis of acoustic sources with controllable near fields in free space and finite depth homogeneous ocean environments. We first present the theoretical results at the basis of our discussion and then, to illustrate our findings we focus on the following three particular examples:1. acoustic source approximating a prescribed field pattern in a given bounded subregion of its near field. 2. acoustic source approximating different prescribed field patterns in given disjoint bounded near field sub-regions. 3. acoustic source approximating a prescribed back-propagating field in a given bounded near field sub-region while maintaining a very low far field signature.For each of these three examples, we discuss the optimization scheme used to approximate their solutions and support our claims through relevant numerical simulations.arXiv:1706.05233v1 [math.OC]

Feasibility analysis for active near/far field acoustic pattern synthesis in free space and shallow water environments

“…In this section, we present a general description of the active manipulation scheme for Helmholtz fields proposed in our previous works. The unified functional and numerical framework have already been discussed in [20,21,35]. We shall briefly recall several essential theoretical results and describe some geometric configurations of interest.…”

“…The problem geometry in these two environments are sketched in Figures 1 and 2. Although the theoretical discussion in [20,21,35] indicates that an arbitrary number of source regions, exterior control regions, and far-field directions can be considered in the active control scheme, here we shall only consider a single source D a , two control regions D 1 , D 2 , and two far-field directions x 1 , x 2 for illustrative purposes. A single source D a b R 3 is modeled as a compact region in both free space and homogeneous ocean.…”

“…These include, but are not limited to, active noise control [2][3][4], personal sound zones or multizone sound reproduction [5][6][7], active acoustic cloaking [2,[8][9][10], remote sensing [11,12] and metamaterial design [13][14][15]. Active sound control techniques are becoming increasingly ubiquitous to enhance sound-based systems [16][17][18][19][20][21]. Forward and inverse problems for sound in underwater environments have been widely studied in the literature (see monographs [22][23][24] and references therein).…”

“…In general, it is fairly difficult to find the analytical fundamental solution *Corresponding author: jchen82@central.uh.edu and thus, in this paper we follow the paradigm proposed in [22] and consider a simpler marine environment modeled as a shallow water or a homogeneous finite-depth ocean. Our sensitivity analysis builds up on the numerical framework developed in [20,21,35]. We use the associated Green's function to represent the solution of the Helmholtz equation and employ the integral equation (IE) method to formulate the forward propagator.…”

An Experimental Method to Determine the Cut-Off Frequency of an Acoustical Free Field in a Non-Ideal Environment

“…2) Near field of a source is the region close to a source [7]. In this region, the sound field does not decrease by 6 dB each time the distance from the source is increased [8].…”