The Department of Defense, specifically the Navy, is seeking innovative solutions through the SBIR program to develop ambient acoustic noise-cancelling technology for military boom microphones used in high-noise environments. The objective is to design devices that effectively reduce ambient noise transmitted through the microphone signal, thereby enhancing speech intelligibility and lowering at-ear noise levels, which is critical for flight safety and mission success. This technology is essential for military aircraft operations, where existing systems do not adequately filter out unwanted noise, and it must be compatible with current communication systems and flight helmets. The solicitation is set to open on April 23, 2025, with proposals due by May 21, 2025, and further details can be found at the provided source link.

## Description

Microphones operating in high-noise environments transmit a significant amount of ambient acoustic noise to the ear in addition to the desired speech signal. This results in higher, and potentially damaging, at-ear noise levels and reduced speech intelligibility. Reducing acoustic noise carried in the electrical microphone signal will lower at-ear noise levels and improve speech intelligibility. There is currently no capability in military aircraft to prevent undesired acoustic noise from entering the boom microphones along with the desired speech signal. The noise is transmitted as part of the electrical signal to the communication system and on to the ear. Noise cancellation technology exists for low-noise environments, such as call centers. Technology needs to be developed for the communications systems and high-noise environments of military aircraft. Solution(s) may include an add-on item in line with the existing microphone or microphone and preamplifier and/or replace the existing microphone or microphone and preamplifier. Solution(s) must be suitable for military aircraft operational use and hardened for the shipboard EMI environment. Noise cancellation is expected to cover the entire operational frequency range of a standard military microphone and preamplifier. Device(s) must be compatible with existing aircraft communication systems, listed in terms of priority, which provide either: <ol><li> 28 VDC to preamplifier (MIL-A-23595D or similar) and 5 Ohm dynamic microphone (MIL-PRF-26542-2E or similar) </li><li> 10 VDC to integrated 150 Ohm electret microphone-preamplifier (MIL-M-49199A or similar) </li><li> No power; 5 Ohm dynamic microphone (MIL-PRF-26542-2E or similar) connected directly to communication system (Solution may be submitted for a subset of these options) </li></ol>It is preferred that the device(s) be powered by existing aircraft power. If battery power is included in the solution, the device must not degrade the communication signal if battery fails. Increase of weight on the head shall be no more than 50 grams. Priority will be given to designs that minimize weight. There shall be no increase in forward center of gravity offset of the system compared to legacy. Additions or changes to boom microphone shape or size must not degrade user visibility. This topic aligns with PMA-202 focus area: Improved Aircrew Communication. Deficient speech intelligibility can lead to errors and omissions in time-critical acts, which jeopardize flight safety and mission success. High intensity ambient noise during aircraft operations, which enters the communications system via the microphones, circumvents hearing protection. <ol><li> Compatible with/adaptable to current flight helmets and communications gear </li><li> Independent of aircraft communications electronics and radios</li></ol>Note: NAVAIR will provide Phase I awardees with the appropriate guidance required for human research protocols so that they have the information to use while preparing their Phase II Initial Proposal. Institutional Review Board (IRB) determination as well as processing, submission, and review of all paperwork required for human subject use can be a lengthy process. As such, no human research will be allowed until Phase II and work will not be authorized until approval has been obtained, typically as an option to be exercised during Phase II.

## Objective

Design device(s) that will provide cancellation of ambient acoustic noise in the electrical signal from a military boom microphone.

## Phase I

Design and build a functional prototype that provides ambient acoustic noise cancellation of the transmitted electrical microphone signal. Verify that the design can reduce pink noise with and without tonal components. Determine the noise reduction achieved in each 1/3 octave band. Verify that the speech signal is not degraded. The Phase I effort will include prototype plans to be developed under Phase II.Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.

## Phase II

Build and deliver operational prototypes suitable for the U.S. Navy to conduct flight testing. This will include validating the design reduces aircraft noise and determine noise reduction achieved in each 1/3 octave band and at tonal frequencies and conducting speech intelligibility testing relative to M-87 microphone and EMI testing. Note: Please refer to the statement included in the Description above regarding human research protocol for Phase II.

## Phase III: Dual Use Applications

Flight test, finalize design, and deliver production units. Transition to PMA-202 and add devices as approved items in the Aviation-Crew Systems, Aircrew Personal Protective Equipment Technical Manual. Noise cancellation of a transmitted electrical microphone signal can be used for any head mounted microphone in a high- or extreme-noise environment. Device(s) can be used or adapted for use in general aviation aircraft.

Ambient Acoustic Noise Cancelling for Military Boom Microphones

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