Acoustic Watermarking for Air ASW Systems

Navy SBIR 24.1 - Topic N241-018
NAVAIR - Naval Air Systems Command
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET

N241-018 TITLE: Acoustic Watermarking for Air ASW Systems

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Computing and Software; Integrated Network Systems-of-Systems; Sustainment

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 an active sonar watermarking capability for Air Anti-Submarine Warfare (ASW) sonobuoy systems that improves wide area search timelines, sonar track localization, and enables communication with other platforms such as Unmanned Underwater Vehicles (UUVs). Additionally, provide some method that indicates that the active transmission is from an authentic source.

DESCRIPTION: Sonar waveform watermarking embeds a digital message into an active sonar transmission so that the receiver can recover information from the transmitter, as well as conduct the usual echo detection and ranging. In future Air ASW systems, many active sonar sources will be operating in close proximity—both time and space—to each other. While this improves detection performance, a means of unambiguously providing detection association to a specific source will improve the system’s track accuracy for a target. This SBIR topic seeks to develop a digital watermarking technology embedding information in each source ping that can be successfully interpreted at low signal-to-noise ratios (SNRs) and can assist in assigning sources to ambiguous echo detections (i.e., detection association).

This technology will reduce sonar search times by at least 25% against fast targets. Watermarking source transmissions will allow more sources to operate simultaneously and unambiguously, while maintaining a high degree of correct echo-to-source association. Watermarking technology will improve the target Area of Uncertainty (AOU) by at least 15% by increasing the number of near simultaneous detections used during target tracking.

The watermarking technology should degrade detection probabilities by less than 1 dB when operating in a wide range of ocean channel conditions, at SNR 2 dB higher than the theoretical Minimum Detectable Level (MDL). The watermarking should degrade Doppler estimation accuracy by less than 5% and range accuracy by less than 10% in realistic ocean channels that include Doppler and time spreading.

The watermarking must be applicable to narrowband waveforms such as Continuous Wave (CW) pulses, and should also be applicable to wideband waveforms such as Frequency Modulated (FM) waveforms.

The same watermarking technology can be used to embed short acoustic communication messages in active sonar transmissions that are received by other platforms in close proximity such as surface ships, and unmanned underwater vehicles even when the receiving platform is operating with high self-noise. These short acoustic communication messages can be a means to provide authentication and transmission assurance.

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 32 U.S.C. § 2004.20 et seq., National Industrial Security Program Executive Agent and Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence and Security Agency (DCSA) formerly Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DCSA and NAVAIR 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 during the advanced phases of this contract IAW the National Industrial Security Program Operating Manual (NISPOM), which can be found at Title 32, Part 2004.20 of the Code of Federal Regulations. Reference: National Industrial Security Program Executive Agent and Operating Manual (NISP), 32 U.S.C. § 2004.20 et seq. (1993).

PHASE I: Develop a digital watermarking technology applicable to wide area search systems to enable successful detection association with a set of at least four sources, maximizing source de-confliction, and being able to clearly identify the source that generated the detection. Demonstrate, using simulations, the watermarking technology does not reduce signal detection by more than 1dB at MDL+2dB. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop a prototype underwater acoustic source that includes embedded watermarks on typical Air ASW waveforms. Develop acoustic software that can be used for at-sea testing. Demonstrate the watermarking technology can successfully identify a specific source from at least 32 different sources. Demonstrate the watermarking technology can successfully transmit and interpret messages at low SNRs.

Work in Phase II may become classified. Please see note in Description paragraph.

PHASE III DUAL USE APPLICATIONS: Make recommendations for this technology to be included into the Production Sonobuoy Specification. Demonstrate during an at-sea data-gathering event the watermarking technology functions as designed. Provide an interface documentation description for the integration of this capability into an active ASW sonobuoy system. This technology will primarily benefit military applications. Surface ship multistatics would benefit from this capability. A commercial application would be to include watermarking into audio files to provide a means of authentication and protection.


  1. Lynch, R., & Mobasseri, B. G. (2013). Using Realistically Simulated Undersea Channels to Evaluate the Performance of Authenticating Sonar.
  2. Lynch, R. S., Carter, G. C., & Mobasseri, B. (2012, February 12). Method for embedding information in sonar (U.S. Patent No. 8,127,138). U.S. Patent and Trademark Office.

KEYWORDS: Watermarking; embedding information; assurance; tracking; detection association; source de-confliction


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 24.1 SBIR BAA. Please see the official DoD Topic website at for any updates.

The DoD issued its Navy 24.1 SBIR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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