This Special Issue focuses on noise associated with advanced air mobility (AAM), an emerging class of predominantly electric distributed-propulsion aircraft designed for urban and regional transportation. As these vehicles move toward certification and deployment, noise has become a central challenge for regulatory approval and public acceptance, particularly due to operations in densely populated areas and at low altitudes. The 24 contributions in this issue address three key aspects of AAM noise: prediction, measurement, and human perception. Prediction studies span a wide range of modeling fidelities, from high-resolution simulations to improved semi-analytical approaches, and examine complex aeroacoustic mechanisms, including rotor interactions, turbulence ingestion, and broadband noise generation. Measurement studies, largely at model scale, provide new insights into tonal and broadband noise characteristics across configurations and operating conditions, while supporting model validation. Perception-focused contributions investigate annoyance, sound quality metrics, and auralization, emphasizing the role of context and operational factors in shaping human response. Together, these works highlight the interdisciplinary nature of AAM noise research and the need for integrated approaches to enable quieter vehicle design.

This work presents a low-order framework to predict aerodynamic interaction and the associated tonal loading noise in closely spaced co-rotating propellers under forward-flight conditions. The modeling approach moves beyond acoustic-interference-based methods by explicitly accounting for rotor–rotor aerodynamic coupling. The wake of each propeller is modeled as a system of de-singularized rigid helical tip vortices, which induce velocity via the Biot–Savart law, both on the generating rotor and on neighboring disks. The formulation relies solely on isolated-propeller forces, computed using blade-element momentum theory. The induced velocity field is used to reconstruct the unsteady inflow and blade loading, with unsteady effects incorporated through a Sears-function-based correction. Comparisons against LB-VLES simulations of three side-by-side propellers show that the model accurately predicts the spatial distribution and phase of the unsteady thrust, with peak locations within approximately 10 ^◦ and amplitude errors of about 30%. The resulting loading is coupled to a rotating-dipole acoustic formulation. At the blade-passing frequency (BPF), the predicted far-field directivity agrees within ±1–4 dB in most directions. The model captures both the aerodynamic source modulation and the resulting constructive and destructive interference patterns in the tonal acoustic field. Owing to its low computational cost, the proposed model enables rapid assessment of installation effects in early design stages, including variations in propeller spacing and relative phase angle.

Laminar to turbulent transition induced by spanwise periodic arrays of cylindrical roughness elements over a NACA 0012 airfoil is investigated by hotwire anemometry and infrared thermography. The roughness elements are placed in the flow under adverse pressure gradient. Three configurations are investigated, namely an isolated roughness element, a spanwise array of roughness elements, and a pair of arrays in stagger. The streamwise and spanwise interactions between roughness wakes are addressed, focusing on the evolution of mean flow features and mechanisms for the subsequent process of laminar-turbulent transition. The spanwise interaction between roughness elements involves the connections and merging of neighboring low-speed regions (MLS) in the wake, which affects the spanwise distribution and amplitude of the velocity streaks. The maximum effect on promoting transition is observed when two neighboring low-speed regions overlap with each other in the near wake (within 6 times roughness height). The addition of a second roughness array promotes transition when the spanwise spacing is larger than two times the roughness diameter. Spectral analysis of the streamwise velocity fluctuations reveals that the number of roughness elements within the spanwise array affects the number of MLSs and the dominant instability mechanism. For an odd number of MLSs, the Kelvin–Helmholtz instability dominates the growth of velocity fluctuations around the three-dimensional shear layers. For an even number of MLSs, both Kelvin–Helmholtz and asymmetric instabilities appear in the wake. In this case, the dominant mode that leads to transition depends on the spanwise spacing between roughness elements.

The Council of European Aerospace Societies (CEAS) Aeroacoustics Specialists Committee (ASC) supports and promotes the interests of the scientific and industrial aeroacoustics community on a European scale and European aeronautics activities internationally. In this context, “aeroacoustics” encompasses all aerospace acoustics and related areas. Each year the committee highlights some of the research and development projects in Europe. This paper is a report on highlights of aeroacoustics research in Europe in 2023, compiled from information provided to the ASC of the CEAS. In addition, during 2023, a number of research programmes involving aeroacoustics were funded by the European Commission. Some of the highlights from these programmes are also summarized in this article, as well as highlights from other projects funded by national governments and industry. Contributions are gathered in sections by topic, and a section covering relevant European scientific events in 2023 is also included. Enquiries concerning all contributions should be addressed to the authors who are given at the end of each subsection.

A high-fidelity aeroacoustic simulation of a full-scale electric vertical take-off and landing vehicle was performed to investigate the transition maneuver from vertical ascent to forward flight. The study employed a Lattice Boltzmann method, enabling the resolution of complex unsteady aerodynamic phenomena while maintaining manageable computational costs. The analysis revealed that aerodynamic interactions between rotors, nacelles, and the wing significantly affect the distribution of aerodynamic forces, with rotor-wing interference playing a key role in lift and drag behavior. Acoustic emissions were evaluated in the far field using a permeable formulation of the Ffowcs Williams-Hawkings analogy on a spherical array representative of an urban air mobility operational context. The results highlighted clear directional patterns and a harmonic-dominated frequency spectrum. The findings offer critical insights into the coupled aerodynamic and acoustic behavior of eVTOLs during transition and provide a high-fidelity reference to support the validation of lower-order design tools.