Directional Acoustic Communications Transmitters

Navy SBIR 22.1 - Topic N221-059
NAVSEA - Naval Sea Systems Command
Opens: January 12, 2022 - Closes: February 10, 2022 (12:00pm est)

N221-059 TITLE: Directional Acoustic Communications Transmitters



The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop directional acoustic transmitters that can be scaled for use on medium, large, and extra-large unmanned undersea vehicles (UUVs).

DESCRIPTION: The Navy seeks to develop directional acoustic transmitters for use on UUVs. The commercial market lacks directional transducers appropriate for UUV integration/usage due to lack of commercial demand/use cases for such a capability. The closest commercial equivalents would be spherical arrays targeted for vertical (in water column) applications, but such arrays are not suitable for the UUV applications targeted by the Navy. Directional acoustic transmitters will enable the Navy to more effectively conduct UUV swarming operations by reducing mutual interference, as well as more clandestine communications by directing the transmitted acoustic beam pattern main response axis (MRA) toward the intended receive array. Current commercial UUV transmit/receive transducers project omni-directional acoustic energy in all directions, whereas directional transmitters are generally limited to larger manned platforms such as submarines. Development of directional projectors compatible with size, weight, and power (SWaP) constraints of UUVs is challenging. The available SWaP within UUVs varies greatly by class and design, but rough order of magnitude (ROM) allowances are provided in the table below. It is noted that the values in this table are provided for guidance only – they are not to be considered formalized requirements against which the proposals will be adjudicated.

UUV Class




ROM Volume:

216 in3 (6" cube)

1728 in3 (12" cube)

5832 in3 (18" cube)

ROM weight in air:

8 lbs

64 lbs

216 lbs

ROM Tx Power:




ROM Standby Power:




These SWaP challenges are exacerbated by the requirement to withstand large hydrostatic pressures experienced during UUV missions. Larger projectors are required to generate narrower/more focused beams, so a prime challenge is optimizing the transmitter to fit within the existing UUV platforms. Another challenge is the pointing of the transmit beam, i.e., its MRA as well as its width while maintaining sidelobe rejection at other angles. For longer ranges (> 1km) acoustic transmission paths are more complex and require knowledge of the environment and a modeling capability. In addition to development of the directional transmitters, proposers should include the pointing method of the resultant beam, control of the beam’s sidelobes and the main lobe width, minimizing size, weight, power, and cooling (SWaP-C) associated with the solution, and the novelty of the approach.

The technical merit of the proposed solutions will be evaluated on factors including:

  1. Ratio of the energy to the targeted region vs. the energy transmitted over the entire (360°) geographic region
  2. Required level of in-situ environmental knowledge in order for the transmitter to point itself and achieve the focused gain described in #1
  3. Transmitter gain over a variety of environmental and bathymetric conditions
  4. Maximum volume and maximum physical or synthetic transmit aperture dimension
  5. Estimated weight of the system
  6. Maximum power draw by the transmitter when in use and during standby
  7. Suitability of chosen projector technology to operate/survive over the variety of operational depths over which PEO-USC UUVs operate

The company will test the prototype system, first in a controlled laboratory environment, then in an in-water (saltwater) environment, to determine its capability to meet all relevant performance metrics outlined in the Phase II SOW. Testing shall characterize the optimization of directional transducer control, coupled with the communication function, in the presence of interfering and mutual interference of external assets. The company shall demonstrate the prototype system performance in both environments (laboratory and in-water) to the Government and present the results in two separate test reports.

Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence Security Agency (DCSA), formerly the Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DCSA and NAVSEA in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract.

PHASE I: Develop a concept for a directional acoustic transmitter that meets the requirements in the Description. Establish feasibility by developing system diagrams as well as Computer-Aided Design (CAD) models that show the transmitter concept and provide estimated weight and dimensions of the concept. Feasibility will also be established by computer-based simulations that show the transmitter’s pointing capabilities are suitable for the project needs. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Based on the results of Phase I and the Phase II Statement of Work (SOW), develop and deliver a prototype system for in-water testing and measurement/validation of the Phase I performance attributes. Test the prototype system, first in a controlled laboratory environment, then in an in-water (saltwater) environment, to determine its capability to meet all relevant performance metrics outlined in the Phase II SOW. Testing shall characterize the optimization of directional transducer control, coupled with the communication function, in the presence of interfering and mutual interference of external assets. Demonstrate the prototype system performance in both environments (laboratory and in-water) and present the results in two separate test reports to the Government. Use the results to correct any performance deficiencies and refine the prototype into a pre-production design that will meet Navy requirements. P Prepare a Phase III SOW that will outline how the technology will be transitioned for Navy use.

It is probable that the work under this effort will be classified under Phase II (see Description section for details).

PHASE III DUAL USE APPLICATIONS: If successful, in addition to UUV applications, these directional acoustic transmitters could be applied to other unmanned Navy assets including buoys and subsea nodes. These assets have communications requirements, some of which require clandestine communications, for which these directional acoustic transmitters could provide a solution. In addition to such DoD applications, these directional acoustic transmitters could be used in commercial oil, gas, and oceanographic sensing applications, where the prevention of mutual interference between submerged assets is required.


  1. Freeman, Simon. "A highly directional transducer for multipath mitigation in high-frequency underwater acoustic communications." The Journal of the Acoustical Society of America 138(2):151-154. August 2015.
  2. Stojanovic, Milica. "Retrofocusing techniques for high rate acoustic communications." The Journal of the Acoustical Society of America Volume 117, 2005: 1173-1185. March 11, 2021
  3. N. Fruehauf and J. A. Rice, "System design aspects of a steerable directional acoustic communications transducer for autonomous undersea systems," OCEANS 2000 MTS/IEEE Conference and Exhibition. Conference Proceedings (Cat. No.00CH37158), Providence, RI, USA, 2000, pp. 565-573 vol.1, doi: 10.1109/OCEANS.2000.881315.

KEYWORDS: Transducers; acoustic communications; clandestine communications; swarming UUVs; mutual interference; beam pointing; in-situ environmental collection.


The Navy Topic above is an "unofficial" copy from the overall DoD 22.1 SBIR BAA. Please see the official DoD Topic website at for any updates.

The DoD issued its 22.1 SBIR BAA pre-release on December 1, 2021, which opens to receive proposals on January 12, 2022, and closes February 10, 2022 (12:00pm est).

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