Noise Emission Research Articles

Research on Battery Electric Vehicles’ DC Fast Charging Noise Emissions: Proposals to Reduce Environmental Noise Caused by Fast Charging Stations

The potential of electric vehicles (EVs) to support the decarbonization of the transportation sector, crucial for meeting greenhouse gas reduction targets under the Paris Agreement, is obvious. Despite their advantages, the adoption of electric vehicles faces limitations, particularly those related to battery range and charging times, which significantly impact the time needed for a trip compared to their combustion engine counterparts. However, recent improvements in fast charging technology have enhanced these aspects, making EVs more suitable for both daily and long-distance trips. EVs can now deal with long trips, with travel times only slightly longer than those of internal combustion engine (ICE) vehicles. Fast charging capabilities and infrastructure, such as 350 kW chargers, are essential for making EV travel times comparable to ICE vehicles, with brief stops every 2–3 h. Additionally, EVs help reduce noise pollution in urban areas, especially in noise-saturated environments, contributing to an overall decrease in urban sound levels. However, this research highlights a downside of DC (Direct Current) fast charging stations: high-frequency noise emissions during fast charging, which can disturb nearby residents, especially in urban and residential areas. This noise, a result of the growing fast charging infrastructure, has led to complaints and even operational restrictions for some charging stations. Noise-related disturbances are a significant urban issue. The World Health Organization identifies noise as a key contributor to health burdens in Europe, even when noise annoyance is subjective, influenced by individual factors like sensitivity, genetics, and lifestyle, as well as by the specific environment. This paper analyzes the sound emission of a broad sample of DC fast charging stations from leading EU market brands. The goal is to provide tools that assist manufacturers, installers, and operators of rapid charging stations in mitigating the aforementioned sound emissions in order to align these infrastructures with Sustainable Development Goals 3 and 11 adopted by all United Nations Member States in 2015.

Effects of leading-edge serration shape on noise reduction in rod-airfoil interactions.

Leading-edge serrations inspired by owls exhibit the capability to control airfoil-turbulence interaction noise, but the design principle of the serration shape is still an open issue. To this end, we designed five types of serration shapes with different combinations of curvature, namely, triangular, ogee, anti-ogee, feather-like, and anti-feather-like. These curves are applied to serrated modifications with different bluntness levels (sharp or blunt) and amplitudes (0.05, 0.075, and 0.1 chord length). Considering these serration shapes, 30 cases with various curved types, bluntness levels, and amplitudes are investigated using compressible large-eddy simulation and the acoustic analogy of Ffowcs-Williams and Hawkings on a rod-airfoil configuration. The outcomes reveal a general trend where increased amplitude and blunted serrations are more effective in noise mitigation. Notably, the blunt feather-like (FB) serrations demonstrate the maximum noise reduction capacity across all amplitude levels, decreasing the overall sound power level by up to 2.1 dB. Through multi-process acoustic analysis, source characteristics responsible for generating noise are diagnosed. It is found that noise reduction primarily stems from the change in the source distribution and destructive interference among sound sources, consistent with prior studies. Generally, the serration shape would significantly affect the source distribution and sound interference without altering the fundamental noise reduction mechanisms. The FB shape exhibits the highest concentration of sources at its peaks and roots among all shapes. The presence of concentrated sources in these locations enhances destructive interference, effectively reducing noise emissions. The superior noise-reduction feature of FB serrations should be attributed to both the concentration of sources and the destructive interference. This extensive examination underscores the importance of serration design, especially the potential of FB serrations, in noise control strategies for rod-airfoil configurations, contributing to advancements in aeroacoustic engineering.

Impact of Power Tiller Noise on the Occupational Health of Indian Farmers: A Case Study of Jammu and Kashmir

Power tillers have significantly improved the efficiency of agricultural operations in India. However, their noise emissions pose considerable health risks to operators. This study investigates the impact of power tiller noise on occupational health, and evaluates the effectiveness of various noise protection devices. Noise levels were recorded at different engine speeds, revealing that without protection, noise could reach 103.14 dB(A), surpassing the recommended safe occupational limit of 85 dB(A). Noise reduction capabilities of ear muffs, ear plugs, and moist cotton were assessed. Ear muffs provided highest noise reduction, lowering noise by 40.50%, followed by ear plugs (32.70%) and moist cotton (26.80%). The physiological impact of noise on operators was also measured, showing that ear muffs led to the most significant reductions in elevated blood pressure (both systolic and diastolic blood pressure) as well as increased heart rate. The findings underscore the urgent need for effective noise mitigation strategies in power tiller operations and recommend ear muffs as the most effective protective device for safeguarding operators’ health.

Racing in Kart Dromes: Laboratory and Site Assessment of Noise Levels from Competition and Rental Karts

Kart racing is one of the hobbies that people get passionate about from a young age. Kart dromes are commonly built in suburban or rural areas, generally surrounded by industrial zones and sporadic residential buildings. The circuits are primarily active during summer, hosting races that often extend into the evening and night hours, where each race has a duration of 20 min. This study examines the noise generated by kart dromes through acoustic measurements conducted at a kart drome located in southern Italy, where a microphone was placed at the side of the circuit for short periods in addition to a survey conducted at the nearest sensitive receptor. Another survey was conducted within the kart drome for a long-term period to record all of the variations in noise levels of a typical summer day when the races are organized during the nighttime; for this type of data, the hourly average values were taken for one week in June, July, and August, highlighting the increasing trend in the noise levels due to the kart races. However, a detailed analysis of noise emissions during different phases of kart operation revealed two significant acoustic events, such as the acceleration of pass-by peaks centered on high frequencies and strong breaking noise at curves that are centered at low-medium frequencies, causing a whistling noise of the wheels while turning the kart. This paper highlights the increasing trend in noise levels during summer nighttime races, compares on-site measurements with laboratory data, and discusses the implications for local communities and noise regulations.

Optimization of Noise Emission Level in Diesel Engine with Biodiesel Application Using Response Surface Methodology

This study used biodiesel to run a single-cylinder direct-injection diesel engine. The palm oil methyl ester is blended in different ratios of up to 20% and tested with different engine speeds and loads for noise level measurement. Mathematical modeling was then developed to correlate responses obtained by the noise levels of the engine components to the factors, including engine speed, engine load, and biodiesel blending percentage. Finally, using the developed models, all the numeric factors were optimized. Modeling results indicated that the significance of factors could vary for the engine components, whereas in this study, the intake phase-related factors showed the significance of all factors. Meanwhile, the optimization results highlighted that the best solution with the highest desirability number to satisfy all the responses was the B20 fuel blend (20% biodiesel fuel and 80% diesel fuel blend by volume) with 1200 rpm of engine speed. In conclusion, the study's outcomes revealed that optimization should be considered in developing a new policy for using biofuel in internal combustion engines.

Induction arrow spatial and temporal variations

The induction arrow C is a characteristic of the variable geomagnetic field at one observation point (x, y) for a certain period T of geomagnetic variations B. It visually describes the magnitude and direction of the deviation of the geomagnetic field vector from the horizontal plane. The induction arrow is nonzero only when the vertical component Bz appears. Bz appears in three cases: 1) electrical conductivity’s horizontal gradients under the surface of the globe; 2) incomplete compensation of the vertical component of the primary field of the ionosphere-magnetosphere source by the secondary field induced in the horizontally layered Earth. The degree of compensation systematically changes during the day, year..., leading to temporal variations in the induction arrow (source effect); 3) the appearance of not-removed noise or lithosphere emission containing Bz. This article presents the spatial and temporal variations of the induction arrows. Real (in-phase) and imaginary (out-of-phase) induction arrows (vertical response functions or tippers) were obtained for every day with proper observations from 1991 to 2014 years for five intervals of periods: 150—300 s, 300—600 s, 600—1200 s, 1200—2400 s, 2400—3600 s, calculated from three components of geomagnetic field recorded at 137 observatories of the global network INTERMAGNET. To reduce the scatter, the daily values were recalculated to monthly values. Such global material from +87° to –88° of geomagnetic latitude was obtained for the first time and its analysis yielded new scientific results. The annual variations (with a period one year) are visible at about 2/3 of the observatories (at the other observatories, they are below the background level of shorter period variations and/or noise). Its amplitude strongly depends on the geomagnetic latitude and sometimes reaches such a high value as 0.4—0.5 (peak-to-peak) at high (>65°) latitudes and varies within 0.01—0.15 at middle and low latitudes. Previous studies at middle latitudes discovered that the annual variations in the northern component Au is positive everywhere (maximum in June, minimum in December) and proposed, as a global source model for the annual variations explanation, the ring current at the height 3―6 Earth’s radii. We discovered that at high latitudes, Au is usually negative. We propose to explain all the observed features of the induction arrow’s annual variations by variations of the ionosphere currents in the aurora zone. 11-year variations are found at ≈30 % of observatories located at all latitudes but more frequently in aurora zones. At a few observatories, trends (monotonous changes in arrows) were found. The largest trend of magnitude 0.2 for all periods was found in southern Greenland, where glaciers have been melting rapidly over the past 30 years, which makes it possible to associate both trends with global warming. In a few aurora observatories of North America trends of magnitude ≈0.1 were noticed. In these same years, the North Magnetic Pole unusually rapidly migrated for 1100 km in 23 years. It can be assumed that these trends are related to changes in the aurora oval position. At geomagnetic latitudes from –78° to +78°, the main harmonic (24 hours=86400 s) of daily variations of the geomagnetic field is always accompanied by at least one higher order harmonic 24/n (n=1÷7). At higher latitudes >78° of both hemispheres only the fundamental 24-hour harmonic is visible. Induction arrow temporal variations create difficulties in determining its constant component used to study the electrical conductivity of the Earth’s crust and upper mantle but can be very useful for geodynamic processes study

On the Mechanism of Lateral Asymmetry of Noise Emission from a Propeller Installed Near a Wing

On the Mechanism of Lateral Asymmetry of Noise Emission from a Propeller Installed Near a Wing

In Situ Operando Indicator of Dry Friction Squeal

In various applications, dry friction could induce vibrations. A well-known example is frictional braking systems in ground transportation vehicles involving a sliding contact between a rotating and a stationary part. In such scenarios, the emission of high-intensity noise, commonly known as squeal, can present human health risks based on the noise’s intensity, frequency, and occurrences. Despite the importance of squeal in the context of advancing urbanization, the parameters determining its occurrence remain uncertain due to the complexity of the involved phenomena. This study aims to identify a relevant operando indicator for predicting squeal occurrences. To this end, a pin-on-disc test rig was developed to replicate various contact conditions found in road profiles and investigate resulting squealing. Each test involves a multimodal instrumentation, complemented by surface observations. It is illustrated that the enhanced thermal indicator identified is relevant because it is sensitive to the thermomechanical and tribological phenomena involved in squealing.

Design of Sonic Cage to attenuate noise in Mines using Sonic Crystal and Melamine Foam

Abstract Sonic crystals (SCs) are structures made of sound scatterers periodically arranged in a square or triangular lattice. Recent research on sonic crystals has demonstrated that they are efficient materials for controlling the propagation of sound. They attenuate sound in certain frequency bands due to Bragg scattering across the periodic scatterers. This range of frequencies is known as the bandgap, and it is found that sound propagation is significantly reduced in this bandgap region. Belt conveyors linked sequentially to create extensive pathways across surface mines contribute significantly to noise pollution. Typically, noise emission regulations are surpassed in areas where these conveyors operate, especially at night. The operation of belt conveyors predominantly contributes to the overall noise produced by the technological infrastructure. Hence, it is crucial to aim at decreasing their noise emissions. So, with an aim to attain elevated noise reduction, various intuitive sonic cage designs made of sonic crystals such as rigid scatterers, resonant scatterers, and multi resonant scatterers were suggested and followed by the calculation of free-field insertion loss (IL). Insertion Loss (IL) refers to the decrease in noise level at a specific location resulting from the installation of a noise control device along the sound path between the sound source and that particular location. The novelty of this work is that a class of periodic structures, called the radial sonic crystals are presented, in polar coordinates. The initial investigation shows the insertion loss of the proposed sonic cage followed by calculation of insertion loss of hybrid sonic cage design using melamine foam.

Multicenter Evaluation of the QIAstat-Dx and the BioFire Multiplex Panel Tests for the Detection of Respiratory Pathogens.

Syndromic multiplex panel testing enables simultaneous detection of multiple respiratory pathogens, but limited data is available on the comparative diagnostic performance of different testing systems. In this multicenter prospective study, we aimed to compare the QIAstat-Dx Respiratory Panel 2.0 (QIAstat-Dx-RP2.0) with the widely used BioFire-RP2.1, using 269 respiratory clinical specimens. Concordant test results were obtained in 232 (86.3%) cases. Discordant test results included 33 BioFire-RP2.1(+)/QIAstat-Dx-RP2.0(-) and 4 BioFire-RP2.1(-)/QIAstat-Dx-RP2.0(+) results. Discordant samples showed significantly lower pathogen loads than concordant ones (p < 0.01). Overall, the QIAstat-Dx-RP2.0 showed an analytical sensitivity of 50%-100% depending on the respiratory target, with an analytical specificity ≥ 99.0%. Most significant differences were found for the detection of adenovirus, human coronaviruses, respiratory syncytial virus, human rhinovirus/enterovirus and SARS-CoV-2 (kappa-score: 0.67-0.91). Co-detections of respiratory pathogens were identified in 47 cases by BioFire-RP2.1 and 29 by QIAstat-Dx-RP2.0. Agreement rates between the two multiplex panel tests decreased from 91.8% for single pathogen detections to 65.0% and 42.9% for co-detecting two and three pathogens, respectively. Pathogen loads were significantly lower in co-detections compared to single pathogen detections (p < 0.01), potentially explaining the lower detection rates with the QIAstat-Dx-RP2.0 in cases of multiple pathogens. In conclusion, our prospective multicenter evaluation showed good diagnostic performance of the QIAstat-Dx-RP2.0 assay, but lower detection rates for some respiratory targets compared to BioFire-RP2.1. As QIAstat-Dx-RP2.0 offers advantages in handling, noise emission, cost effectiveness, and provides semi-quantitative results compared to BioFire-RP2.1 an updated version with enhanced analytical sensitivity would be a viable alternative syndromic testing system for detecting respiratory pathogens.

Pseudorotation Adjoint-Based Aerodynamic and Aeroacoustic Optimization Method for Isolated Rotors

The present study proposes a pseudorotation adjoint-based aerodynamic and aeroacoustic optimization method for the application on isolated rotors with both accuracy and efficiency. The pseudorotation adjoint-based optimization methodology incorporates two innovative techniques: i) a hybrid computational fluid dynamics–computational aeroacoustics method closely integrating with Reynolds-averaged Navier–Stokes equations under a rotating reference frame within a pseudorotation moving-medium Ffowcs Williams-Hawkings formulation to evaluate aerodynamic performance and tonal noise, and ii) a unified architecture for steady-state adjoint-based sensitivity analyses of both aerodynamics and aeroacoustics leveraging the pseudorotation approach, thereby facilitating effective multi-objective weighted optimizations within one comprehensive framework. The proposed pseudorotation steady adjoint-based optimization method is applied to a bidiscipline optimization problem of rotor blades compared with our previous on-the-fly unsteady adjoint method. Results of the comparative study demonstrate that the pseudorotation steady approach exhibits good agreement with the unsteady approach in predicting aerodynamics and aeroacoustics as well as their sensitivity derivatives. Furthermore, the steady adjoint optimization demonstrates its capability in achieving an optimum rotor design that closely resembles the outcome from unsteady adjoint optimization while exhibiting a 20-fold acceleration in computational time. These results highlight the potential of this proposed pseudorotation adjoint-based optimization method in efficiently exploring fundamental principles governing high aerodynamic performance and low tonal noise emissions for isolated rotors.

Towards sustainable freight transportation in Africa: Complementarity of the fuzzy Delphi and best-worst Methods

The focus on sustainable freight transportation (SFT) is crucial for a sustainable future, especially with the African Continental Free Trade Area agreement. However, comprehensive research on the environmental, social, and economic aspects of SFT in Africa is limited. This study integrates the Fuzzy Delphi Method (FDM) and Best-Worst Method (BWM) to evaluate 17 determinants of SFT in Africa, revealing greenhouse gas emissions, noise emissions, and accident risk as the most significant challenges. The findings and recommendations will guide professionals and policymakers to implement proactive measures to address challenges in the freight transportation market for a more sustainable future.

Relationship Between Road Traffic Composition and Noise Emission: an Investigation Based on Hungarian National Public Road Traffic Data

Different vehicles contribute to the noise emission of the total road traffic in different ways and degrees. Therefore, emission calculation methods classify road vehicles based on their typical noise emission parameters. This article investigated the role of the four vehicle categories of CNOSSOS-EU method (light motor vehicles, medium heavy vehicles, heavy vehicles, and powered two-wheelers) in generating road traffic noise emissions. Based on traffic data available for national public roads in Hungary, the proportion of each vehicle category in the total road traffic was determined, providing the average distribution and other statistical parameters for each road category. The impact of changes in the traffic composition on noise emission was analysed based on the statistical parameters. The results show the dominance of light vehicles for all road categories (76–89% on average). The average proportion of heavy vehicles is also significant on controlled-access highways (motorways: 21%, expressways: 15%) and main roads (9%). The deviation from the average traffic composition can cause a noticeable difference in road traffic noise emission (up to nearly 3 dB). It was found that the impact of changing the proportion of heavy and light vehicles on noise emission is higher on roads inside built-up areas.

Analysis of the Vibration Effect on the Trailing Edge Noise for Wind Turbine Applications

The noise emitted is a factor in determining the location for installing wind turbines. It can be a concern for people living near wind farms due to the nuisance and health problems caused by noise emissions. Therefore, noise estimation is one of the most relevant aspects of wind turbine design. Aerodynamic noise can be caused by air motion around the turbine blades. This can create a swooshing or whooshing sound as the blades pass through the air. Aerodynamic noise tends to be more prominent at higher wind speeds when the turbine is operating at full capacity. The trailing edge noise is the main source of wind turbine aerodynamic noise. In this work, semi-analytical solutions for modeling this effect are used. The Ffowcs Williams and Hawkings (FW-H) acoustic analogy is used to predict far-field noise generated by wind turbine blades moving in the air. The equations of the rotor–tower–nacelle structure are obtained by the classical finite element method for a typical onshore wind turbine to predict the blade vibration signal. This new formulation is applied to rotating sources and statistical analysis of broadband trailing edge noise. The novelty of this work is to model the acoustic–structure interaction between the wind flow and the blade structure vibration. In this context, the acoustic far-field pressure emissions are modified by source vibration. In this point, this work compares the acoustic pressure values from rigid and flexible sources. Once the relationship between acoustic emission and wind turbine structural vibration is determined, the potential application of this research is, for example, to provide valuable information about the health and integrity of the blades. Thus, the goal of this work is to predict the aerodynamic noise of a typical large wind turbine taking into account its structural behavior. Therefore, Formulation 1A is used to calculate the far-field noise radiated from the trailing edge of wind turbine blades in a low Mach number flow. The vibration effects are input variables to evaluate the intensity and acoustic pressure values. Some computational aspects are discussed and the numerical model is clarified. The acoustic predictions are validated with analytical results and experimental measurements that are available in the scientific literature. The numerical results of the FW-H acoustic analogy demonstrate that the aerodynamic noise value is predominantly low frequency in the sections closest to the source.

Exploring the role of nanoparticle additives in reducing emissions in compression ignition engine

The paper discusses the growing environmental issues caused by vehicle emissions, leading many countries to tighten their emission standards to reduce the harmful gases released by motor vehicles. This is especially important as urbanization has increased, leading to more consumption of petroleum products. As a result, there is a growing need for cleaner, more sustainable fuel alternatives. Biodiesel has been recognized as a potential solution since it is renewable, non-toxic, and less environmentally harmful than traditional diesel. The study in question explores how adding biodiesel and nanoparticles affects diesel engine performance, particularly in terms of noise and particulate matter emissions (small particles of pollution). The research was carried out using a compression ignition engine (like those found in diesel vehicles) under constant RPM (revolutions per minute) and variable loads (changes in engine stress or power requirements). The results showed that when biodiesel was blended with nanoparticles and used as fuel, there was a noticeable reduction in noise levels, carbon dioxide (CO2), and particulate matter emissions compared to regular diesel. This suggests that biodiesel, especially when enhanced with nanoparticles, can effectively lower the harmful effects of diesel engines on the environment, offering a greener and quieter alternative.

Control of Large Wind Energy Converters for Aeroacoustic Noise Mitigation with Minimal Power Reduction

The population is often opposed to wind turbines being erected near their homes, mainly because the machines are noisy, especially at night. In an effort to establish a compromise between the needs of the people and the fulfilment of energy demands, wind turbines have the ability to switch between day and night operation by reducing the rotation speed during the night, resulting in a loss of generated power. The present study investigates simple models for noise emission, propagation, and prediction, with the objective of proposing a control system configuration that continuously adjusts the rotational speed as much as necessary until it matches sound level regulations while minimising power losses. Thus, several approaches are implemented and tested with a very large reference wind turbine. The simulation results of a reference wind turbine show that the approaches provide significant improvements in sound reduction as well as in power conversion.

A Numerical Investigation on the Aeroacoustic Noise Emission from Offshore Wind Turbine Wake Interference

Offshore wind turbine (WT) wake interference will reduce power generation and increase the fatigue loads of downstream WTs. Wake interference detection based on aeroacoustic noise is believed to solve these challenges in offshore wind farms. However, aeroacoustic noise is closely related to the aerodynamics around WT blades, and the acoustic detection method requires the mastery of noise emission characteristics. In this paper, FAST.Farm, combined with the acoustic model in OpenFAST, is utilized to investigate the acoustic noise emission characteristics from two 3.4 MW-130 WTs with wake interference. Multi-microphone positions were investigated for the optimal reception selection under 8 m/s and 12 m/s wind speeds with a typical offshore atmospheric turbulence intensity of 6%. The numerical simulation results indicate that wake deficit reduces the total noise emission by about 6 dBA in the overall sound pressure level (OASPL) at 8 m/s, while wake turbulence marginally increases it and its fluctuation. There is a mutual influence between these effects, and the wake deficit effect can be 100% compensated for in the OASPL at 12 m/s. Additionally, downstream observer locations are suggested based on comparisons. These investigations provide new insights into wake interference in offshore wind farms.

Correction: Appraising machine learning algorithms in predicting noise level and emissions from gasoline-powered household backup generators

Correction: Appraising machine learning algorithms in predicting noise level and emissions from gasoline-powered household backup generators

Holographic method of under-water noise source localization in shallow water

The results of a high-frequency experiment for the detection and direction estimation of underwater sound noisy source are presented. The experiment was conducted in the shallow waters of the Black Sea coast. The noise emission of the source was received by three vector-scalar receivers located on the bottom. By using holographic processing, the detection and direction estimation of a moving underwater source against the background of intense shipping in the experiment region were carried out. Estimates of the input signal-to-noise ratio are presented.

The Effect of Entropy Waves Features on the Indirect Noise Generation within an Aeronautical High-Pressure Turbine stage

Abstract First stages of aeronautical high-pressure turbine are subjected to inlet distortions generated by the combustor systems. Such disturbances, characterized by velocity and temperature fluctuations, are referred to as vorticity and entropy waves and they are convected downstream by the main flow. Such disturbances interact with the turbine stages affecting the stage efficiency, heat exchange and generating noise emissions. This work summarizes a comprehensive numerical campaign on the effect of different Entropy Waves features (i.e. radial position, clocking and swirl direction) on the indirect noise generation of engine-representative high pressure turbine stage tested at the Politecnico di Milano LFM (Laboratory of Fluid Dynamics of Turbomachinery). The numerical campaign is based on URANS CFD simulations with time-varying inlet distortions, carried out with the University of Florence in-house TRAF code. A Discrete Fourier Transform (DFT) based post-processing tool has been used to extract the low frequency entropy wave content to assess indirect noise emissions. The extensive validation of the TRAF code in previous campaigns grants the fidelity of the results in terms of aerodynamic and acoustic quantities. The numerical results provide a deeper insight of the effect of entropy waves features on indirect noise generation. The outcome of the results may be used by the designer to better understand the combustor-turbine interaction, also considering the possible introduction of innovative fuels such as hydrogen or Sustainable Aviation Fuel (SAF).