Patent Description:
In an underwater environment, locating and tracking object with the use of GPS or other RF signals is not practical, as high frequency radio waves do not propagate through water. Accordingly, ultra-short baseline (USBL) underwater acoustic positioning systems are used for accurately locating and tracking various objects of interest in an underwater environment. An underwater acoustic positioning system typically includes a submersible transmitter that is, for example, mounted on the bottom of a ship, and a transponder that is on the seafloor or mounted to some other underwater object of interest. An acoustic signal is transmitted by the ship-mounted transmitter and detected by the object's transponder, which replies with its own acoustic pulse. A ship-mounted transducer, then, detects the return acoustic pulse. The USBL system measures the time from transmission of the initial acoustic pulse until the reply is detected and converts this measurement into a range. Additionally, the angle from the transceiver to the underwater object may be calculated. In this way, the USBL system is capable of accurately locating and tracking the object in the underwater environment.

<NPL>, discloses a sound velocity correction method for underwater acoustic positioning systems. The underwater acoustic positioning system comprises an array of receivers.

A compact, integrated acoustic localization and communications array is disclosed herein. The compact, integrated acoustic localization and communications array consists of a volumetric, USBL transducer array, referred to herein as the "volumetric acoustic array," and integrated acoustic communications transmitter, referred to herein as "transmit unit," integrated and packaged together in close proximity to form a low-volume form factor. Specifically, the compact, integrated acoustic localization and communications array may be provided in a package having dimensions as small as <NUM> centimeters (<NUM> inches) by <NUM> centimeters (<NUM> inches). The compact, integrated acoustic localization and communications array, therefore, provides advantageous size, weight and power (SWAP) for small form-factor applications.

Specifically, the compact, integrated acoustic localization and communications array consists of a plurality of receiver elements precisely positioned at their minimum required baseline separation. The plurality of receiver elements, which together form a volumetric acoustic array, are integrated in a packaging having a small form factor with the transmit unit to form the compact, integrated acoustic localization and communications array having joint acoustic communications (ACOMMs) and localization capability. Additionally, a method of manufacturing the compact, integrated acoustic localization and communications array consistently achieves the required baseline separation of the receiver elements, as well as their required separation from the transmit unit and any surface to which it is mounted, so as to avoid interference that may be caused.

According to a first aspect of the invention, a compact, integrated acoustic localization and communications array, comprising: an air-backed transmit element having a first end on which an end cap is disposed, and a second end configured to be mounted to a mounting surface; and a volumetric acoustic array including a plurality of receiver elements electrically integrated to the transmit element with the end cap between the plurality of receiver elements and the first end; wherein the compact, integrated acoustic localization and communications array is configured to transmit, via the transmit element, and receive, via the plurality of the receiver elements, an acoustic signal having a frequency, the frequency being in the range of <NUM> to <NUM>; and wherein each of the plurality of receiver elements is spaced apart from the end cap at least a first distance, the first distance being greater than ¼ of a wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array, and the first distance not being equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array.

According to an embodiment of any paragraph(s) of this summary, the volumetric acoustic array is a tetrahedral acoustic array.

According to an embodiment of any paragraph(s) of this summary, the plurality of receiver elements are ultra-short baseline receiver elements.

According to an embodiment of any paragraph(s) of this summary, the plurality of receiver elements include lead titanate.

According to an embodiment of any paragraph(s) of this summary, the integrated array is secured in a molding material to preserve the spacing of each of the plurality of receiver elements relative to the end cap.

According to an embodiment of any paragraph(s) of this summary, the molding material is a urethane.

According to an embodiment of any paragraph(s) of this summary, the molding material has a maximum diameter that is less than or equal to <NUM> centimeters and a maximum height that is less than or equal to <NUM> centimeters.

According to an embodiment of any paragraph(s) of this summary, the air-backed transmit element is cylindrical.

According to another aspect of the invention, a system comprising a mounting surface and a compact, integrated acoustic localization and communications array according to the first aspect mounted to the mounting surface: wherein each of the plurality of receiver elements is spaced apart from the the mounting surface at least the first distance; and wherein each of the plurality of receiver elements are spaced apart from the mounting surface at least a second distance, the second distance being greater than ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array, and the second distance not being equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array.

According to another aspect of the invention, a method of assembling a compact, integrated acoustic localization and communications array, the compact, integrated acoustic localization and communications array including an air-backed transmit element having a first end on which an end cap is disposed and a second end configured to be mounted to a mounting surface, the compact, integrated acoustic localization and communications array also including a volumetric acoustic array including a plurality of receiver elements electrically integrated to the transmit element with the end cap between the plurality of receiver elements and the first end, the method comprising the steps of: positioning the plurality of receiver elements relative to each other in a first mold fixture to form the volumetric acoustic array of the plurality of receiver elements; securing the position of each of the plurality of receiver elements relative to each other in the mold fixture with a molding material to preserve the volumetric acoustic array of the plurality of receiver elements; positioning the preserved volumetric acoustic array relative to the end cap of the air-backed transmit element in a second mold fixture to form the compact, integrated acoustic localization and communications array; and securing the position of the preserved volumetric acoustic array relative to the end cap of the air-backed transmit element with the molding material to preserve the compact, integrated acoustic localization and communications array; wherein the compact, integrated acoustic localization and communications array is configured to transmit, via the transmit element, and receive, via the plurality of the receiver elements, an acoustic signal having a frequency, the frequency being in the range of <NUM> to <NUM>; and wherein the step of positioning the preserved volumetric acoustic array includes positioning the preserved volumetric acoustic array relative to the end cap such that each of the plurality of receiver elements in the volumetric acoustic array is spaced apart from the end cap at least a first distance, the first distance being greater than ¼ of a wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array, and the first distance not being equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array.

In an embodiment of the method, the method further includes the step of mounting the second end of the air-backed transmit element to the mounting surface. The step of positioning the preserved volumetric acoustic array relative to the end cap of the air-backed transmit element also includes positioning the preserved volumetric acoustic array relative to the mounting surface such that each of the plurality of receiver elements are spaced apart from the mounting surface at least a second distance. The second distance is greater than ¼ of a wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array, and the second distance is not equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array. The step of securing the position of the preserved volumetric acoustic array relative to the end cap of the air-backed transmit element also includes securing the position of the preserved volumetric acoustic array relative to the mounting surface with the molding material.

According to an embodiment of any paragraph(s) of this summary, the first mold fixture includes a plurality of sockets. Each socket is configured to receive one of the plurality of receiver elements. The step of positioning the plurality of receiver elements relative to each other includes a step of placing each of the plurality of receiver elements into their respective one of the plurality of sockets.

According to an embodiment of any paragraph(s) of this summary, the step of securing the position of each of the plurality of receiver elements relative to each other includes a step of pouring the molding material into the first mold fixture to fill the first mold fixture having the plurality of receiver elements positioned therein.

The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

The annexed drawings show various aspects of the invention.

Referring now to the figures, and initially to <FIG> depicts a general schematic of an exemplary USBL underwater acoustic localization and communications system <NUM>. Specifically, a compact, integrated acoustic localization and communications array <NUM>, which will be described in more detail herein and referred to as "the integrated array <NUM>," may be submerged and mounted on a mounting surface <NUM>. In the illustrated embodiment, the mounting surface <NUM> is located on the bottom of a vessel <NUM> on the surface of a body of water. The integrated array <NUM> is configured to transmit a first acoustic signal <NUM> into the underwater environment. The acoustic signal <NUM> transmitted by the integrated array <NUM> may be received by at least one underwater object <NUM> having a transponder thereon. Upon receipt of the first acoustic signal <NUM>, the transponder on the at least one underwater object <NUM> responds by transmitting a second acoustic signal <NUM> back to the integrated array <NUM>. The integrated array <NUM> is configured to receive the second acoustic signal <NUM>. The USBL underwater acoustic localization and communications system <NUM> is capable, therefore, of accurately measuring and calculating the position and distance of the at least one underwater object <NUM> relative to the integrated array <NUM>.

Turning now to <FIG>, the integrated array <NUM> will be described in more detail. The integrated acoustic array <NUM> includes a volumetric acoustic array <NUM> and an acoustic communication transmit element <NUM>, which are configured to be integrated and packaged together in a low volume form factor. The transmit element <NUM> may be an air-backed, ceramic transmit element. That is, the transmit element <NUM> may have a structure and shape that is backed by air and mechanically isolated from the end cap and mounting surface with corprene (mixture of cork and neoprene). The air-backed transmit element <NUM> may operate more efficiently and have better directionality than, for example, a transmit element having a fluid filled cavity. In the illustrated embodiment, the air-backed transmit element <NUM> is cylindrical and has a hollow core at its axis. Other suitable structures and shapes for the transmit element <NUM> may include, for example, hemispherical, planar or spherical. In any embodiment, the transmit element <NUM> may be configured to transmit acoustic signals in a substantially omni-directional manner. The transmit element <NUM> may have a height that is <NUM> centimeters (<NUM> inches).

In the illustrated embodiment, the air-backed ceramic transmit element <NUM> has a first end <NUM> on which an end cap <NUM> is disposed. The end cap <NUM> is configured to have a plurality of leads, or terminals (not shown), to which wires are connected to electrically couple each of the plurality of receiver elements <NUM> in the volumetric acoustic array <NUM> to the transmit element <NUM>. The configuration and attachment of the wires to the leads, and the electrical integration to the plurality of receiver elements <NUM> to the transmit element <NUM>, depending on application, will be understood by those having ordinary skill in the art. For example, the wires may be connected differently according to the polarity of the ceramic elements. In the illustrated embodiment of <FIG>, there is a seal ring <NUM> disposed between the transmit element <NUM> and the end cap <NUM>. The seal ring <NUM> provides mechanical isolation between the end cap <NUM> and the transmit element <NUM>, as well as a waterproof seal to prevent intrusion of water, or molding material (as will be introduced and described later), into the integrated acoustic array <NUM>. In an embodiment, the seal may be made out of corprene (mixture of cork and neoprene). The air-backed transmit element <NUM> has a second end <NUM> configured to be mounted to the mounting surface <NUM>.

The volumetric acoustic array <NUM> includes a plurality of ceramic receiver elements <NUM>, such as USBL receiver elements, which are configured to be electrically coupled to the transmit element <NUM> via wires and the leads on the end cap <NUM>, as previously described. The plurality of receiver elements <NUM> may, specifically, be made of lead titanate. The plurality of receiver elements <NUM> are positioned in a volumetric, or non-coplanar, configuration to together form the volumetric acoustic array <NUM>. In the illustrated embodiment, the receiver elements <NUM> are positioned relative to each other in a tetrahedral configuration. The tetrahedral configuration is depicted in isolation in <FIG>. In this tetrahedral configuration, including four receiver elements <NUM>, three of the four illustrated receiver elements <NUM> are arranged in a same plane, and the remaining receiver element <NUM> is centrally positioned in a different plane, together forming the tetrahedral configuration. In other embodiments, the receiver elements <NUM> may be positioned in different volumetric, or non-coplanar, configuration.

The integrated array <NUM> is configured to transmit, via the transmit element <NUM>, and receive, via the plurality of receiver elements <NUM> in the volumetric acoustic array <NUM>, an acoustic signal having a frequency up to <NUM>. For example, the integrated array <NUM> may be configured to transmit and receive an acoustic signal having a frequency in the range of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>.

In the illustrated embodiment, wherein the receiver elements <NUM> are positioned relative to each other in a tetrahedral configuration, the baseline separation between co-planar receiver elements <NUM> is ½ of a wavelength associated with the frequency transmitted and received by the integrated array <NUM>. The baseline separation between the non-coplanar element <NUM> and each of the co-planar elements <NUM> may be slightly under ½ of the wavelength associated with the frequency. The specific criteria for required baseline separation of receiver elements in a tetrahedral configuration is described in Beaujean et al.

In the integrated array <NUM>, each of the plurality of receiver elements <NUM> are spaced apart from the end cap <NUM> at least a first distance d<NUM>. The first distance d<NUM> is greater than ¼ of a wavelength associated with the frequency transmitted and received by the integrated array <NUM>. The first distance d<NUM> also is not equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>.

The position of each of the plurality of receiver elements <NUM> in the volumetric acoustic array <NUM> may be secured and preserved in a molding material <NUM>, as depicted in <FIG>. The spacing of each of the plurality of receiver elements <NUM> relative to the end cap <NUM> may also be secured and preserved in the molding material <NUM>, as depicted. The molding material may be, for example, a urethane such as polyurethane PR-<NUM>. It will be appreciated, however, that other types of urethanes may be used. The molding material <NUM>, securing and preserving the elements of the integrated array <NUM>, when hardened, may have a maximum diameter that is less than or equal to <NUM> centimeters (<NUM> inches) and may have a maximum height that is less than or equal to <NUM> centimeters (<NUM> inches). Accordingly, the molding material <NUM> may serve as the small form factor packaging for the integrated array <NUM>.

Now turning to <FIG>, the integrated array <NUM> may be mounted to a mounting surface <NUM>. In the illustrated embodiment, the second end <NUM> of the transmit element <NUM> is mounted to the mounting surface <NUM>. A layer of coprene (mixture of cork and neoprene) may be disposed between the second end <NUM> of the transmit element <NUM> and the mounting surface <NUM> so as to provide mechanical isolation between the transmit element <NUM> and the mounting surface <NUM>. As described earlier with reference to <FIG>, the mounting surface <NUM> may be, for example, located on the bottom of a vessel <NUM> on the surface of the water, or submerged in the water. As depicted in <FIG>, the mounting surface <NUM>, more specifically, may be a surface of a housing <NUM>. The housing <NUM> may have a cavity <NUM> therein for housing various electronic components that are to be coupled to the integrated array <NUM>.

Each of the plurality of receiver elements <NUM> are spaced apart from the mounting surface <NUM> at least a second distance d<NUM>. The second distance d<NUM> is also greater than ¼ of a wavelength associated with the frequency transmitted and received by the integrated array <NUM>. The second distance d<NUM> also is not equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>.

Generally, the second distance d<NUM> must be sufficient to minimize destructive interference that occurs from sound pressure reflection off the mounting surface <NUM>. This is particularly relevant when the acoustic array in the integrated array <NUM> is volumetric, such as the volumetric acoustic array <NUM> described herein, as spacing from each of the plurality of receiver elements <NUM> to the mounting surface <NUM> will not be the same. Discerning an optimal second distance d<NUM>, therefore, may consist of computing the nulling frequency for each of the plurality of receiver elements <NUM> and selecting the second distance d<NUM> such that nulls do not occur in the frequency band of interest (i.e., the frequency at which the integrated array <NUM> is configured to transmit and receive acoustic signals).

Where c is the speed of sound in water and n is an odd number, the nulling frequency, fn, is defined as: <MAT>.

In the illustrated embodiments in which the volumetric acoustic array <NUM> is a tetrahedral acoustic array, the optimal second distance d<NUM> may be discerned for the receiver element <NUM> that is positioned closest to the mounting surface <NUM>, which may be considered the reference point. Where the distance between the reference point and the remaining receiver elements <NUM> is defined as the third distance d<NUM> (<FIG>), the second distance d<NUM> is discerned with explicit consideration of the third distance d<NUM>, such that nulls do not occur in the frequency band of interest with respect to any receiver element <NUM> in the volumetric acoustic array <NUM>.

With reference to <FIG>, an example result is depicted of discerning an optimal second distance d<NUM>, with explicit consideration of the third distance d<NUM>, by evaluating the nulling frequency fn with the above equation for a tetrahedral acoustic array in the integrated array <NUM> configured to transmit and receive an acoustic signal having a frequency in the range of <NUM> to <NUM>. As illustrated in this example, the excluded values for the second distance d<NUM> are where the plotted separation function is equal to zero (i.e., where nulls at the desired frequency will occur). The values between these regions correspond to acceptable ranges for the second distance d<NUM>. As illustrated in this example, while accounting for the distance taken up by the transmit element (dotted vertical line), as well as with explicit consideration of the third distance d<NUM>, the closest range for the second distance d<NUM> in which no nulls will occur is between <NUM> centimeters (<NUM> inches) and <NUM> centimeters (<NUM> inches).

In use, the integrated array <NUM> is capable of transmitting and receiving an acoustic signal in a substantially omni-directional manner. For example, with reference to <FIG>, an exemplary beam pattern for the integrated array <NUM> is depicted, representing a measure of the integrated array <NUM> performance. The outermost beam line represents the composite beam pattern of all <NUM> receiver elements <NUM> in the tetrahedral configuration and the innermost beam line represents the beam pattern of the transmit element <NUM>. As depicted, the integrated array <NUM> achieves a substantially omni-directional operation performance in the lower hemisphere.

Now turning to <FIG>, a method <NUM> of assembling the integrated array <NUM> (<FIG>) will be described. The integrated array <NUM>, as previously described, includes the air-backed transmit element <NUM> (<FIG>) having the first end <NUM> (<FIG>) on which the end cap <NUM> (<FIG>) is disposed and the second end <NUM> (<FIG>) configured to be mounted to the mounting surface <NUM> (<FIG>). The integrated array <NUM> also includes the volumetric acoustic array <NUM> (<FIG>) including the plurality of receiver elements <NUM> (<FIG>) electrically integrated to the transmit element <NUM>.

The method <NUM> includes, at step <NUM>, positioning the plurality of receiver elements <NUM> (<FIG>) relative to each other in a first mold fixture to form the desired configuration of volumetric acoustic array <NUM> (<FIG>) of the plurality of receiver elements <NUM>. At step <NUM>, it will be appreciated that the receiver elements will already be pre-wired according to their required electrical connection to the transmit element. The first mold fixture may have a plurality of sockets, each configured to receive one of the plurality of differential receiver elements <NUM> therein. In an embodiment in which a tetrahedral acoustic array <NUM> is to be formed, the first mold fixture may have three sockets disposed in the same plane at the base of the mold fixture for receiving three of the receiver elements <NUM>, while the fourth receiver element <NUM> is held in place in the mold fixture by a set screw therein. The set screw for receiving and holding the fourth receiver element may be, for example, centrally positioned in the mold fixture in a different plane than the three sockets at the base of the mold fixture. The step <NUM> of positioning the plurality of receiver elements <NUM> relative to each other in the first mold fixture may therefore include placing each of the plurality of receiver elements into their respective one of the plurality of sockets, or set screw, in the first mold fixture.

At step <NUM>, the method <NUM> includes securing the position of each of the plurality of receiver elements <NUM> (<FIG>) relative to each other in the mold fixture with the molding material <NUM> (<FIG>) to preserve the desired configuration of the volumetric acoustic array <NUM> (<FIG>) of the plurality of receiver elements <NUM>. For example, the step <NUM> of securing the position of each of the plurality of receiver elements <NUM> relative to each other may include pouring the molding material <NUM> into the first mold fixture, having the plurality of receiver elements <NUM> positioned therein, to fill the first mold fixture. With brief reference to <FIG>, an exemplary volumetric acoustic array <NUM>, after having been secured in the molding material <NUM> at step <NUM> of the method <NUM> to form a section of the integrated array <NUM> (<FIG>) is depicted. As illustrated, each of the plurality of receiver elements <NUM> are secured in their respective positions relative to each other in the molding material <NUM> and will remain secured in their positions relative to each other throughout the remainder of the method <NUM> of assembly the integrated array <NUM>. Stated differently, the volumetric acoustic array <NUM>, with the precise spacing of receiver elements <NUM> relative to each other, will be preserved.

The method <NUM> additionally includes, at step <NUM>, positioning the preserved volumetric acoustic array <NUM> (<FIG>) relative to the end cap <NUM> (<FIG>) of the air-backed transmit element <NUM> (<FIG>) in a second mold fixture to form the integrated array <NUM> (<FIG>). The second mold fixture may include a "U" fixture plate of specific thickness and keying features that align the volumetric acoustic array <NUM> to the correct height off the mounting plate <NUM>, d2, and heading that orients volumetric acoustic array <NUM> relative to the chosen frame of reference.

As described earlier, the integrated array <NUM> (<FIG>) that is assembled by the method <NUM> is configured to transmit, via the transmit element <NUM>, and receive, via the volumetric acoustic array <NUM> (<FIG>) of the plurality of receiver elements <NUM> (<FIG>), an acoustic signal having a frequency up to <NUM>. For example, the integrated array <NUM> may be configured to transmit and receive an acoustic signal having a frequency in the range of <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM>, or <NUM> to <NUM>.

The step <NUM> of positioning the preserved volumetric acoustic array <NUM> (<FIG>) includes positioning the preserved volumetric acoustic array <NUM> relative to the end cap <NUM> (<FIG>) such that each of the plurality of receiver elements <NUM> (<FIG>) in the volumetric acoustic array <NUM> are spaced apart from the end cap at least the first distance d<NUM>. As previously described, the first distance d<NUM> is greater than ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>. The first distance d<NUM> also is not equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>.

At step <NUM>, the method <NUM> includes securing the position of the preserved volumetric acoustic array <NUM> (<FIG>) relative to the end cap <NUM> (<FIG>) of the air-backed transmit element <NUM> with the molding material <NUM> (<FIG>) to preserve the integrated array <NUM>.

The method <NUM> may additionally include mounting the second end <NUM> (<FIG>) of the air-backed transmit element <NUM> (<FIG>) to the mounting surface <NUM> (<FIG>). In this embodiment, the step <NUM> of positioning the preserved volumetric acoustic array <NUM> (<FIG>) relative to the end cap <NUM> (<FIG>) of the air-backed transmit element <NUM> includes positioning the preserved volumetric acoustic array <NUM> relative to the mounting surface <NUM> such that each of the plurality of receiver elements <NUM> are spaced apart from the mounting surface <NUM> at least a second distance d<NUM>. As previously described, the second distance d<NUM> is also greater than ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>. The second distance d<NUM> also is not equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the integrated array <NUM>.

In this embodiment, the step <NUM> of securing the position of the preserved volumetric acoustic array <NUM> (<FIG>) relative to the end cap <NUM> (<FIG>) of the air-backed transmit element <NUM> (<FIG>) includes securing the position of the preserved volumetric acoustic array <NUM> relative to the mounting surface <NUM> (<FIG>) with the molding material <NUM> (<FIG>). With brief reference to <FIG>, an exemplary integrated array <NUM> is depicted, with the second end <NUM> of the air-backed transmit element <NUM> being mounted to the mounting surface <NUM> and the position of the preserved volumetric acoustic array <NUM> being positioned and secured relative to both the end cap <NUM> and the mounting surface <NUM> by the molding material <NUM>.

The method <NUM> may additionally include a step <NUM> of forming a smooth profile of the formed integrated array <NUM> with more of the molding compound. This step <NUM> is performed with the use of a third fixture mold to achieve the maximum dimensions (diameter and height) of the integrated array <NUM>. An exemplary integrated array <NUM> assembled according to the method <NUM> described herein is depicted in <FIG>. As illustrated, the integrated array <NUM> assembled according to the method <NUM> may have a maximum diameter that is less than or equal to <NUM> centimeters (<NUM> inches) and may have a maximum height that is less than or equal to <NUM> centimeters (<NUM> inches).

Claim 1:
A compact, integrated acoustic localization and communications array (<NUM>), comprising:
an air-backed transmit element (<NUM>) having a first end (<NUM>) on which an end cap (<NUM>) is disposed, and a second end (<NUM>) configured to be mounted to a mounting surface (<NUM>); and
a volumetric acoustic array (<NUM>) including a plurality of receiver elements (<NUM>) electrically integrated to the transmit element with the end cap between the plurality of receiver elements and the first end;
wherein the compact, integrated acoustic localization and communications array is configured to transmit, via the transmit element, and receive, via the plurality of the receiver elements, an acoustic signal having a frequency, the frequency being set in the range of <NUM> to <NUM>; and
wherein each of the plurality of receiver elements is spaced apart from the end cap at least a first distance (d<NUM>), the first distance being greater than ¼ of a wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array, and the first distance not being equal to an odd multiple of ¼ of the wavelength associated with the frequency transmitted and received by the compact, integrated acoustic localization and communications array.