N252-093 TITLE: Ambient Acoustic Noise Cancelling for Military Boom Microphones
OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Integrated Network Systems-of-Systems
OBJECTIVE: Design device(s) that will provide cancellation of ambient acoustic noise in the electrical signal from a military boom microphone.
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:
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.
1. Compatible with/adaptable to current flight helmets and communications gear
2. Independent of aircraft communications electronics and radios
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.
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.
REFERENCES:
KEYWORDS: Microphone; Noise cancelling; Noise cancellation; Noise reduction; Speech intelligibility; Communication
** TOPIC NOTICE ** |
The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 25.2 SBIR BAA. Please see the official DoD Topic website at www.dodsbirsttr.mil/submissions/solicitation-documents/active-solicitations for any updates. The DoD issued its Navy 25.2 SBIR Topics pre-release on April 2, 2025 which opens to receive proposals on April 23, 2025, and closes May 21, 2025 (12:00pm ET). Direct Contact with Topic Authors: During the pre-release period (April 2, 2025, through April 22, 2025) proposing firms have an opportunity to directly contact the Technical Point of Contact (TPOC) to ask technical questions about the specific BAA topic. The TPOC contact information is listed in each topic description. Once DoD begins accepting proposals on April 23, 2025 no further direct contact between proposers and topic authors is allowed unless the Topic Author is responding to a question submitted during the Pre-release period. DoD On-line Q&A System: After the pre-release period, until May 7, 2025, at 12:00 PM ET, proposers may submit written questions through the DoD On-line Topic Q&A at https://www.dodsbirsttr.mil/submissions/login/ by logging in and following instructions. In the Topic Q&A system, the questioner and respondent remain anonymous but all questions and answers are posted for general viewing. DoD Topics Search Tool: Visit the DoD Topic Search Tool at www.dodsbirsttr.mil/topics-app/ to find topics by keyword across all DoD Components participating in this BAA.
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| 4/26/25 | Q. | TPOCs for topic N252-093 provide the following FAQs (PART 1 of 2): |
| A. | Q: What is the population who will use this?
A: This topic was written to include pilots and aircrew in rotary and fixed wing aircraft that use boom microphones. Tactical aircraft that primarily use a mask microphone and maintainer microphones are not included, but these cases could be future areas of development. Q: Do we need to design a single solution for all cases? A: The solution can be one design that covers all three electrical configurations or multiple designs that address the three cases. Solutions may also address a subset of the three cases. Q: What is the acoustic environment? A: We have measured up to 118 dBA in aircraft. Testing is expected to be done at 105 and 120 dB with and without tonal components. We expect to provide noise files to companies selected for Phase I. Q: What do the existing circuits for the three cases look like? A: See diagrams on this link of the existing circuits for the three cases - navysbir.com/n25_2/N252-093-Circuits.pdf Q: What are the characteristics of the electrical signal expected by the aircraft communication system? A: All cases require an analog signal to the aircraft communication system. For case 1, which is used in most aircraft we are seeking a solution for, the MIL-A-23595/1-2 preamplifier is specified to deliver a nominal level of 250 millivolts (RMS) and maximum undistorted level of 900 millivolts (RMS) into a 100 Ohm load. For case 2, the MIL-M-49199A (model M-162) integrated microphone amplifier is specified to deliver a nominal level of 18 millivolts (RMS) into a 150 Ohm load. For case 3, aircraft getting signal directly from the MIL-PRF-26542/2E (or similar) microphone (model M-87, 5 Ohm not 150 Ohm) is specified to deliver a nominal level of 250 microvolts (RMS) into a 5 Ohm load. Q: What is the supply power provided by the aircraft communication system to the microphone preamplifier? A: For case 1, which is used in most aircraft we are seeking a solution for, the MIL-A-23595/1-2 preamplifier is specified to operate on 27.5 VDC bias voltage, with a nominal operating range of 22 to 30 VDC, and to draw less than 20 mA DC input current. For case 2, the MIL-M-49199A (model M-162) integrated microphone amplifier is specified to operate on 10 +/- 2 VDC bias voltage and to draw less than 8 mA DC input current. For case 3 no supply power is provided. How much power is available to operate additional circuitry is unknown and expected to vary between different aircraft. Q: Is there a requirement for latency? A: Latency shall be not perceptible, <10 ms. |
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| 4/26/25 | Q. | TPOCs for topic N252-093 provide the following FAQs (PART 2 of 2): |
| A. | Q: If a battery is used in the solution, is there a requirement for battery life?
A: If a battery is used in the solution, battery life threshold is >12 hours, objective is 20 hours. Q: What are the main helmets/headsets this will be used on? A: Helmets: HGU-68, HGU-56, and HGU-84. Headsets: Aviation headsets, e.g., David Clark similar, with microphone electrical characteristics of the three cases. Q: Where is the preamplifier located? A: It is typically installed on the side of the helmet. Q: Which speech intelligibility metrics are preferred? Is human subject testing required? A: The ANSI S3.2 Modified Rhyme Test (MRT) is the DoD’s ‘gold standard’ for speech intelligibility qualification and airworthiness. Other measures can and are expected to be used during development. Q: Can a solution modify aircraft components? A: No, the solution must be integrated on the person. There are no options to modify aircraft systems. Q: What are the EMI requirements? A: We expect any solution to meet the same MIL-STD-461 design limits as for the existing microphone and preamplifier, described in MIL-A-23595 and MIL-M-49199A. Components qualified for use in the USN environment generally must pass EMI testing at 200 V/m. Q: What issues have you had with previous efforts? A: A previous microphone evaluated for Navy use did not operate well in wind. The solution must perform as well or better than the M-87 microphone in wind. A second microphone was found to be electrically incompatible. Q: We are having problems getting to the referenced files – can they be provided? A: The MIL specifications are available for free through Assist Quick Search (https://quicksearch.dla.mil/qssearch.aspx). We unfortunately cannot share ANSI S3.2 as that is a licensed document, available from ANSI (webstore.ansi.org). |