The U.S. Navy is seeking innovative solutions for non-wearable, off-engine jet noise reduction (JNR) technologies to mitigate the significant noise produced by afterburning jet engines during various operational phases, including ground testing and takeoff. The objective is to develop a system that achieves substantial noise reduction (10dB+ desired) in the audible frequency range, particularly below 5kHz, while ensuring compatibility with current operating environments and minimizing infrastructure modifications. This initiative is crucial for enhancing operational efficiency and reducing the negative health and environmental impacts associated with jet noise. Interested parties can find more information and submit proposals through the official solicitation link, with the application due date set for February 5, 2025.

## Description

The U.S. Navy seeks a non-wearable, off-engine JNR solution to address the significant noise generated by afterburning jet engines during ground and indoor testing, aircraft taxiing, takeoff, and landing operations. Current state-of-the-art noise reduction technologies consist of:<ul><li> Barriers and headsets that attenuate and reflect sound</li><li> Active sound sources that reduce noise through destructive interference </li><li> A combination of the previous two principles</li></ul>Engine mounted noise reduction technologies have been explored in the past, but such state-of-the-art solutions for tactical aircraft tend to negatively impact thrust performance while providing little noise reduction benefit for low bypass turbofan and turbojets, which makes them undesirable in a military application. Passive and Active Noise Control (ANC) equipped headsets are known to significantly reduce perceived jet noise levels, but they are insufficient for mitigating the sound emanating from modern afterburning engines. Further headset noise reduction can be accomplished through more invasive earpieces, but they come with other challenges. To further reduce perceived jet noise levels, the Navy is interested in non-wearable, off-engine, jet noise reduction technologies that complement the benefits of modern headset. This STTR topic focuses on:<ul><li> Developing advanced noise reduction techniques that can be implemented off-engine and benefit a broad coverage area</li><li> Delivering a flexible solution that addresses the noise signatures of various U.S. Navy jet engines</li><li> Developing a system that delivers noise reduction at the necessary amplitudes and frequency ranges needed to be effective</li><li> Ensuring compactness and compatibility with current operating environments, minimizing need for infrastructure modifications</li><li> Creating a solution that is energy efficient to minimize the burden of powering the system during extended operations</li><li> Utilizing robust, durable technologies that can survive the harsh thermal, acoustic, vibratory, corrosive, and EMF environment of an aircraft carrier</li></ul>Solutions should aim to:<ul><li> Achieving significant noise reduction (10dB+ desired) in the audible frequency range, especially at frequencies below 5kHz</li><li> Providing tonal and broadband noise reduction</li></ul>The resulting technology should:<ul><li> Function effectively at relevant distances from the jet engine exhaust centerline</li><li> Be compact, lightweight, and portable to minimize impact on fleet operations.</li><li> Be easily deployable, requiring a reasonable amount of time for setup and activation in various environments</li><li> Operate reliably for extended periods of time in a typical Naval operating environment, which may consist of extreme weather and highly corrosive conditions</li><li> Have broad application across engine operating range at various power levels</li><li> Be responsive to rapid changes in engine power or acoustic disturbances</li><li> Be responsive to changing noise source positions and environmental factors that influence acoustic propagation</li><li> Ensure that noise is not increased beyond acceptable levels in an undesirable location</li></ul>Example candidate technologies may include, but are not limited to:<ul><li> Off-Aircraft, distributed sound generators that synchronize with jet noise to destructively interfere at desired locations</li><li> On-Aircraft, but off-engine, distributed sound generators that destructively interfere with jet noise</li><li> Temporary fluid-based barriers, such as water/bubbly water curtains, that significantly attenuate/reflect/scatter jet noise with minimal impact to personnel/aircraft mobility. These fluid-based barriers should be sufficiently far from the jet plume to avoid interaction.</li></ul>Please note that the Navy is not interested in the following types of technologies for this topic:<ul><li> Passive or dynamic solid barriers</li><li> Passive or active noise cancelling headsets/headphones</li><li> On-aircraft water injection system that interact with jet plume</li><li> Engine, or nozzle, mounted flow actuators, tabs, or chevrons</li></ul>

## Objective

Develop and demonstrate a non-wearable, off-engine, jet noise reduction (JNR) solution that is capable of significantly reducing afterburning turbofan/turbojet jet noise levels during testing, ground and test cell operations, and take-off and landing events, thereby reducing the negative health and environmental impacts associated with jet noise.

## Phase I

Determine the feasibility and develop a concept for a non-wearable, off-engine jet noise reduction prototype system. The awardee will be expected to perform modeling and simulation to identify and design an innovative approach that meets the specified noise reduction, operational range, portability, and durability requirements. Phase I efforts should include the following:1) Define and develop a detailed concept for the noise reduction system, including the underlying hardware, sensors, software, methodologies, and their integration. 2) Perform modeling and simulation to demonstrate the feasibility of the proposed concept in achieving the desired noise reduction within the specified parameters.3) Develop a preliminary design for the prototype system, outlining key components, system architecture, and expected performance. 4) Provide a detailed report summarizing the concept development, feasibility analysis, and preliminary design. This report should include: a) Technical approach and innovation, b) Simulation results and analysis, c) Design specifications and proposed materials/components, and d) Implementation plan for Phase 2, including a projected timeline, milestones, and budget estimates.The Phase I effort should culminate in a proof-of-concept demonstration, through simulation or fundamental testing, that substantiates the proposed technology&rsquo;s potential and justifies further investment in Phase II.

## Phase II

Develop, demonstrate, and validate a fully functional prototype of the non-wearable, off-engine, jet noise reduction solution based on the concept and feasibility analysis conducted in Phase I. Phase II efforts should include the following:1) Use the results from Phase I to design and fabricate a prototype system that meets the specified noise reduction, operational range, portability, and durability requirements.2) Conduct testing to validate the performance of the prototype in reducing jet engine noise. Testing should first be carried out in a controlled environment and later in a realistic environment. The demonstration should showcase the system&rsquo;s effectiveness, ease of use, and operational reliability.3) Provide detailed documentation of the prototype development efforts including hardware/software design, performance models, and simulation/test results.4) Deliver a final report summarizing the development, demonstration, and validation of the prototype.Phase II efforts should result in a validated prototype that demonstrates the capability to significantly reduce jet noise in a broad defined area.

## Phase III: Dual Use Applications

Focus on the commercialization and deployment of the proposed technology within the U.S. Navy and other potential defense and civilian applications. The technology will become fully operational, validated, and production ready in Phase III and will be capable of significantly reducing jet noise levels during ground and indoor testing, aircraft taxiing, takeoff, and landing operations. The primary use cases for this technology beyond Phase II will be at Navy jet engine test facilities, on naval aircraft carriers and at Naval bases where jet noise is a significant concern. This technology has significant commercialization potential because it is applicable to commercial test facilities and airports as well. This technology could also be beneficial for powerplants and other industrial applications that use gas turbine engines.

Non-Wearable and Off-Engine Jet Noise Reduction

STTR Opportunity Analysis

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