The United States (U.S.) has invested significantly in further understanding the acoustics of Emerging Technology Aircraft in the form of research programs, working groups, symposiums, workshops, technical committee meetings, and data measurement campaigns – see selected references below. For example, the U.S. Federal Aviation Administration (FAA) measured seven ETA models in late 2021 using a large microphone array and data processing programs that were created to better understand the acoustics of these aircraft. The U.S. expects to be able to share some results of these measurements and research in the CAEP/13 cycle.
The FAA has also been actively developing a certification basis for ETA seeking a type certificate from the U.S. Since many of these aircraft do not align well with Annex 16 Volume 1 or 14 CFR part 36 due to their design and operating specifications, the FAA is developing a rule of particular applicability (RPA) for each aircraft model as the FAA builds its noise databases for these aircraft types. To that end, the FAA published a final rule of particular applicability for the Matternet Model M2 aircraft in September of 2022. The FAA sees the development and publication of RPAs as positive steps toward the eventual development of a general rule (or rules) for UAS noise certification. Regarding UAM, the FAA expects to follow a similar approach for aircraft that do not align with 14 CFR Part 36.
In parallel to noise certification of ETA designs, the United States is also conducting environmental reviews of Federal Actions associated with ETA (e.g. operational approvals), which include noise impact assessments.
NASA AAM Mission Overview https://www.nasa.gov/aam
NASA Technical Report - UAM Noise: Current Practice, Gaps and Recommendations https://ntrs.nasa.gov/citations/20205007433
ASCENT Project 049: Modeling of UAM Noise https://ascent.aero/project/modeling-of-urban-air-mobility-noise-to-enable-innovative-means-of-noise-reduction/
ASCENT Project 077: Measurements to Support Noise Certification for UAS/UAM Vehicles https://ascent.aero/project/measurements-to-support-noise-certification-for-uas-uam-vehicles-and-identify-noise-reduction-opportunities/
US DOT Volpe Center UAS Noise Research https://www.volpe.dot.gov/AC-Cert/UA-noise-research
INCE USA Technology for a Quieter America Workshop Reports on UAS Noise Control and Air Mobility https://www.inceusa.org/publications/technology-for-a-quieter-america/
NASA AAM National Campaign https://www.nasa.gov/aamnationalcampaign
VFS Workshop on eVTOL Infrastructure: Acoustics and Noise https://www.youtube.com/watch?v=4SRS98uWEa0