10:30
Session 15: UAS/UAM noise regulations 1
Chair: Zoltan Bazso
10:30
20 mins
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UAS-NoiseCheck – Comparing EASA Drone Noise Measurements Using Ground-Based and Microphone Array Approaches
Matin Blass, Stefan Grebien, Franz Graf
Abstract: Unmanned aerial systems (UAS) are increasingly deployed in civil airspace, making their acoustic impact a key factor for public acceptance and regulatory approval. In response to the absence of standardized in-flight noise assessment procedures, the \textit{European Union Aviation Safety Agency} (EASA) introduced guidelines for UAS noise measurements in 2022, which are currently being evaluated in terms of their practical applicability and measurement uncertainty. In this paper, we present the results of the \textit{UAS-NoiseCheck} project, a multimodal measurement system developed to implement and extend the EASA measurement concept. The system combines acoustic sensing and tracking with optical and GNSS reference data as well as meteorological measurements, enabling synchronized traceable in-flight noise characterization. In addition to the single inverted ground-based reference microphone as specified in the EASA guidelines, the setup incorporates a hemispherical 32-microphone array to enable spatially resolved acoustic analysis. The work focuses on a quantitative comparison of sound pressure level metrics derived from these two approaches. Specifically, we compare the A-weighted sound exposure level (LAE) and the equivalent continuous sound pressure level (LAeq) values obtained from the inverted ground-based microphone with levels extracted from array-based beamforming signals for multiple multicopter UAS under controlled flight conditions. The results demonstrate systematic differences between the measurement concepts, highlight the influence of source directivity and flight dynamics, and provide insight into the transferability of array-based noise metrics to regulatory sound level indicators. These findings contribute to the ongoing discussion on standardized UAS noise assessment by evaluating the consistency, limitations, and added value of microphone array measurements within the context of EASA-compliant noise certification and future drone noise monitoring concepts.
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10:50
20 mins
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Noise Assessment in Support of the Programmatic Environmental Assessment for Drone Package Delivery Operations in the United States
Brandon Robinette
Abstract: The National Environmental Policy Act (NEPA) is the United States’ basic national charter for protection of the environment. It is intended to ensure Federal agencies consider the environmental impacts of their actions in the decision-making process. The Federal Aviation Administration’s (FAA) policies and procedures for compliance with NEPA are contained in USDOT Order 1050.1D DOT’s Procedures for Considering Environmental Impacts and FAA Order 1050.1G FAA National Environmental Policy Act Implementing Procedures.
NEPA requires Federal agencies to assess the environmental effects of proposed major Federal actions prior to making decisions. Major FAA actions include authorizations issued to operators of Unmanned Aircraft Systems (UAS) to enable unmanned aircraft (UA; also referred to as a drone) operations in the national airspace system (NAS). One type of UAS operation is using drones to deliver goods to customers (referred to as package delivery). The FAA has completed 23 environmental assessments (EAs) for individual drone package delivery proposals and one programmatic environmental assessment (PEA) for statewide drone package deliveries. Each EA resulted in a finding of no significant impact (FONSI).
To support the environmental review process for UAS package delivery proposals throughout the United States (U.S.), the FAA and HMMH have prepared a PEA in accordance with NEPA, FAA Order 1050.1G, and USDOT Order 5610.1D. The FAA intends to use the PEA to comply with its NEPA requirements for subsequent requests for authorizations from individual drone operators proposing to conduct package delivery operations in areas of the U.S.
In coordination with the FAA, HMMH developed the noise exposure analysis process for drone package delivery operations used in the PEA. The noise analysis process is described in the report Noise Assessment for Package Delivery Operations with Unmanned Aircraft in the United States (Robinette, 2025) included as Appendix C to the PEA. The document presents the methodology for, and estimation of noise exposure related to the operation of UA for package delivery operations within the U.S. under Title 14 Code of Federal Regulations Part 135. The methodology has been developed with data provided by current Part 135 UA package delivery operators and the FAA to date. Results of the noise analysis are presented in terms of SEL for individual delivery cycles and DNL extents based on varying levels of potential operations for areas at ground level below each phase of the flight.
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11:10
20 mins
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On the Influence of Measurement Configuration for UAS Noise Characterisation
Dale Lambert
Abstract: Standardised methods for aircraft noise measurement and assessment have been developed over several decades to support the evaluation and regulation of conventional civil aviation and are increasingly being applied to unmanned aircraft systems (UAS) as their use expands across a range of applications. However, UAS differ fundamentally from conventional aircraft in terms of operating altitude, vehicle mass, source–receiver proximity, and noise characteristics, including features known to influence human perception and annoyance. These differences raise important questions regarding the suitability of measurement techniques developed for larger aircraft when applied to UAS noise characterisation.
Laboratory-based measurements are commonly used to characterise noise sources under controlled conditions; however, as UAS increase in size and operational complexity, such measurements can become difficult to implement and may not fully capture acoustic features associated with free-flight operation. As a result, ground-based outdoor measurements are often required to characterise UAS noise under representative conditions. Many recommended outdoor measurement approaches specify multi-channel microphone arrays and microphone mounting practices, such as upright or inverted microphones positioned above ground boards using fixed supports. While intended to ensure repeatability for conventional aircraft measurements, these approaches can introduce practical and logistical challenges for UAS applications. Simplified microphone mounting arrangements and reduced-channel measurement configurations may therefore offer more practical alternatives, but their influence on derived acoustic metrics has not yet been systematically examined.
This work examines how measurement configuration choices influence the characterisation of UAS noise, with the aim of informing approaches that are technically defensible, practically feasible, and scalable to support evolving patterns of UAS deployment. Such considerations are essential if noise assessment methods are to remain relevant for evaluating human exposure and perception, and for supporting the development and interpretation of future guidance and regulatory frameworks for UAS noise.
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