The increasing number of electric vehicles on roads has led to concerns about their safety signals. A recent study from Chalmers University of Technology in Sweden has found that one of the most common signal types is difficult for humans to locate, especially when multiple similar vehicles are moving simultaneously.

Researchers conducted a study involving 52 test subjects who were placed at the center of anechoic chambers and surrounded by loudspeakers. Three types of simulated vehicle sounds were played on the loudspeakers, corresponding to signals from one, two or more electric and hybrid vehicles, plus an internal combustion engine. The test subjects had to mark the direction they thought the sound was coming from as quickly as possible.

The results showed that all signal types were harder to locate than the sound of an internal combustion engine. One type of signal, which consisted of two tones, was particularly difficult for the test subjects to distinguish, with many unable to determine whether it was one or multiple vehicles emitting the sound.

This study highlights a hidden flaw in electric vehicle safety and emphasizes the need for further research into how people react in traffic situations involving electric vehicles. The researchers suggest that new signal types may be needed to improve detection and localization, while minimizing negative impacts on non-road users.

The study’s findings have implications for policymakers and car manufacturers, who must balance the need for effective safety signals with the potential consequences of noisy environments.

As the number of electric vehicles on roads continues to grow, it is essential that safety considerations are prioritized. This study serves as a reminder of the importance of continued research into the acoustic properties of electric vehicle safety signals.

The world of glass appears deceptively simple – a seemingly random network of atoms. However, recent research at the University of Tsukuba has shed light on the existence of a “hidden order” within this disorderly structure. This invisible arrangement plays a crucial role in determining vibrational fluctuations in the terahertz (THz) frequency range, which significantly impact the physical properties of glass.

At first glance, glass may seem like a jumbled mess of atomic structures. Yet, when subjected to X-ray and neutron beam analysis, a faint but consistent periodic feature known as the first sharp diffraction peak (FSDP) emerges. Concurrently, glass exhibits a boson peak (BP), a vibrational anomaly in the THz range that contributes to its low thermal conductivity, mechanical characteristics, and THz range light absorption. Despite extensive research, the precise relationship between the FSDP and BP has remained unclear – until now.

Using heterogeneous elasticity theory, researchers have identified a direct correlation between the emergence of the BP and the presence of the FSDP. The theoretical model indicates that the scale of elastic inhomogeneity necessary for BP manifestation aligns with that of the FSDP. This suggests that the FSDP is a determining factor in the vibrational behavior of glasses within the THz band.

These groundbreaking findings are expected to inform the development of novel glass materials with tunable boson peaks, enabling targeted control of their thermal and mechanical properties. By unlocking the secrets of the hidden order in glass, researchers can now explore new possibilities for creating materials with tailored properties, opening doors to innovative applications across various industries.

The world is on the cusp of a revolution in aviation, with emerging electric aircraft engines promising to change the game. However, a significant challenge remains – their noise levels can be gratingly unpleasant. A groundbreaking study conducted by scientists at the University of Bristol and the University of Salford has finally uncovered the root cause behind this issue and identified potential solutions.

The research, published in Nature npj Acoustics, delves into the physics of aerodynamic sound generation, revealing how turbulent boundary layer flow interacts with rotating fan and duct components to produce two distinct and perceptually unpleasant acoustic signatures. The team discovered that these noise patterns, known as “haystacking,” are caused by the interaction between turbulent flow and the internal acoustic field of the engine.

At low thrust levels, the weaker fan suction allows the airframe boundary layer flow to remain undisturbed, resulting in duct haystacking. In contrast, at high thrust levels, strong fan suction disrupts the airframe boundary layer flow, producing fan-induced flow distortion that draws in highly-unsteady turbulent flow structures across a larger portion of the blade span.

Lead researcher Dr. Feroz Ahmed highlighted the significance of this study: “These two hidden sound signatures – haystacking – make future embedded aircraft engines feel perceptually irritating, not just loud.” By understanding the aerodynamic origin of these noise patterns, engineers can now design quieter engines that truly sound as quiet as they look.

The implications of this research are far-reaching. The team’s findings offer actionable design guidance for both large-scale transport aircraft and manufacturers of next-generation electric vertical take-off and landing (eVTOL) aircraft in the urban air mobility sector. These insights could help reduce aircraft noise by 65% and support efforts to meet the EU’s FlightPath 2050 goal.

The researchers now plan to develop aerodynamic and acoustic control strategies to reduce both fan and duct haystacking, with the aim of shaping the future of quiet aviation.