10:30
UAS/UAM noise regulations
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 standardised in-flight noise assessment procedures, the 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 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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Correction curves for multirotor unmanned aircraft system noise measurement using ground-board mounted microphone
Xianghao Kong, Michael Kingan, Huachen Zhu
Abstract: Accurate noise characterization of multirotor unmanned aircraft systems (UAS) in outdoor tests is complicated by ground reflections that bias measured sound pressure levels (SPL) and directivity patterns. Ground-board mounted microphones provide a practical, low-profile measurement option for low-altitude UAS noise tests, but they require robust, frequency-dependent corrections to recover free-field-equivalent source levels for certification-style reporting. This paper develops correction curves that translate ground-board mounted microphone measurements into free-field-equivalent levels across frequency and observer angle, while preserving the directional features of multirotor noise across representative flight modes.
The correction strategy is anchored by an indoor reference dataset acquired in an anechoic chamber using ISO-aligned procedures across hover, yaw, slow cruise, ascent, and descent. A multi-microphone array spanning a wide range of polar angles is used to resolve radiation directivity, and ISO-recommended A-weighted metrics are computed for both stationary (SPL) and moving (sound exposure level and, where needed, slow-time-weighted maximum SPL) flight modes. Statistical convergence is quantified using accumulated confidence intervals from repeated trials, providing an experimentally grounded baseline for repeatability and for assessing far-field suitability.
To quantify ground-induced bias for a ground-board configuration, the UAS is represented as a compact vertical dipole above a finite-impedance half-space. Frequency-dependent surface-impedance models representative of common outdoor grounds (e.g., grassland and concrete) are used to predict excess attenuation relative to free field as a function of frequency, source height, and observer angle on practical angular grids, with levels distance-normalized to a 1 m reference. These predictions are converted into correction curves (ΔL) that can be applied directly to ground-board spectra and overall noise metrics.
The outcome is a set of experimentally anchored, geometry-aware correction curves, together with geometry and repeat-count guidance, that enables repeatable ground-board UAS noise measurements while reducing sensitivity to site-specific ground conditions and supporting ISO-consistent reporting across multiple flight modes.
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11:30
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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11:50
20 mins
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Flight test campaign following the new EASA Guidelines on noise measurement of UAS
Nico Van Oosten, Luis Meliveo, Silviu Emil Ionescu
Abstract: In 2023 EASA issued the “Guidelines on Noise Measurement of Unmanned Aircraft Systems Lighter than 600 kg Operating in the Specific Category (Low and Medium Risk)”. These guidelines provide a harmonized methodology to perform the noise flight tests and data analysis procedures. In order to gain experience with this methodology so as to provide an optimal service to its customers, ANOTEC performed a noise test campaign with several of its drones at its test site in Motril-Granada (Spain). This paper describes the equipment used, the tests and data analysis performed and an overall assessment of the methodology.
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12:10
20 mins
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Indoor Drone Noise Impact on European Buildings: The Role of Façade Insulation and Stand-Off Distance for Urban Operations
Marco Oliveira, John Kennedy
Abstract: The integration of drones into European civilian sectors necessitates a comprehensive assessment of their noise effects on both natural and built environments. Although much has been learned about drone noise from aeroacoustic and human-response studies, its direct impact on indoor environments remains poorly understood. This gap is critical, as indoor acoustic quality is a key determinant of occupant health and well-being. Specifically, the penetration of drone noise indoors hinges on the building envelope's design, the drone's operational and emission profile, and its proximity to the structure. This work quantifies the minimum facade sound insulation and stand-off distances required to ensure acoustic comfort in typical European residences from a hovering drone, accounting for variations in construction systems, altitude, and proximity. Using in-flight measurement data, we accurately captured the sound power of a delivery drone with a payload capacity of 2.5 kg. The outdoor noise propagation from a drone to receivers at 2 meters from the façade was modelled. These results were used to model indoor noise levels in a typical bedroom for various facade typologies and to determine the minimum drone-to-facade stand-off distances required to meet a target of 30 dB(A). The findings show that for D2m,nTw ranging from 33 to 40 dB, the required stand-off distance varied dramatically. With windows closed, the required distances ranged from 2.5 meters for Nordic constructions to 37.5 meters for Mediterranean ones. When windows were open, these distances escalated to between 190 and 295 meters, regardless of the facade typology. Furthermore, the persistence of distinct tonal peaks reaching 36 dB(A) at 100 Hz in lightweight building systems, when overall broadband noise targets are met, underscores the potential inadequacy of single-number metrics for characterizing the nature of drone noise. The presented framework provides essential guidelines to inform future urban drone noise regulations. It supports the establishment of evidence-based stand-off distance limits, facade insulation standards, and specific tonal-noise criteria to safeguard indoor acoustic comfort.
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