Calculation Of Noise Research Articles

Traffic Noise Absorption and Propagation in A Three-Dimensional Spatial Environment

The impact of noise barriers on noise propagation is vital for traffic noise calculations and visualizations. Noise barriers create a major noise reduction. Green belts are the most common type of noise barrier to mitigate road traffic noise. The width, height, and surface area of leaves a green belt, as well as the noise absorption coefficient of leaves, are vital for noise absorption. This review aims to compare the characteristics and performance of green belts barriers built for traffic noise reduction. Individual tree canopies play the main role in absorbing noise in green belts. Therefore, identifying the canopy's properties is important. The side scan and nadir scan from the LiDAR survey were used to detect the tree canopy points cloud. The voxel-based, convex hull, and concave hull methods are used to visualize tree canopies in three-dimensional (3D). Concave hull provides an extract fitting surface than convex hull visualization. However, these hull surfaces do not provide accurate estimation of surface area of leaves. Further, voxel-based horizontal layers through the voxel-based profiling describes a significant method to calculate surface area of leaves in tree canopies. Establishing green belts as barriers is more cost-effective, making the former better for developing countries.

Traffic Noise Absorption and Propagation in A Three-Dimensional Spatial Environment

The impact of noise barriers on noise propagation is vital for traffic noise calculations and visualizations. Noise barriers create a major noise reduction. Green belts are the most common type of noise barrier to mitigate road traffic noise. The width, height, and surface area of leaves a green belt, as well as the noise absorption coefficient of leaves, are vital for noise absorption. This review aims to compare the characteristics and performance of green belts barriers built for traffic noise reduction. Individual tree canopies play the main role in absorbing noise in green belts. Therefore, identifying the canopy's properties is important. The side scan and nadir scan from the LiDAR survey were used to detect the tree canopy points cloud. The voxel-based, convex hull, and concave hull methods are used to visualize tree canopies in three-dimensional (3D). Concave hull provides an extract fitting surface than convex hull visualization. However, these hull surfaces do not provide accurate estimation of surface area of leaves. Further, voxel-based horizontal layers through the voxel-based profiling describes a significant method to calculate surface area of leaves in tree canopies. Establishing green belts as barriers is more cost-effective, making the former better for developing countries.

Influence of Free Surface on the Hydrodynamic and Acoustic Characteristics of a Highly Skewed Propeller

The noise analysis of a large-scale aquaculture vessel reveals that during its navigation, the primary equipment noise, particularly from the propeller, exerts a notable influence on the aquaculture environment for large yellow croaker. The free surface greatly impacts the noise performance of propellers, which is a significant factor affecting the fish’s habitat. This study adopts the numerical simulation method to analyze the hydrodynamic and acoustic characteristics of the E1619 propeller operating near the free surface. The open-water performance and noise calculations of the propeller are verified through experiments, and the effects of different immersion depths and advance coefficients on the propeller are explored. The results demonstrate that the free surface significantly affects the thrust, torque, and noise of the propeller, especially at shallow immersion depths and low advance coefficients. Surface wave pattern causes the instability and breakup of tip vortices, causing increased thrust and torque fluctuations, reduced efficiency, and significant overall sound pressure levels in the entire flow field. As immersion depth and advance coefficients increase, the interaction between tip vortices and the free surface weakens, wake vortex instability decreases, and noise levels gradually reduce. These analyses and conclusions can guide the design of next-generation propellers for aquaculture vessels to optimize performance near the free surface.

STUDY OF AERODYNAMIC NOISE OF PROPELLER CONSIDERING THE INFLUENCE OF BOUNDARY SURFACE USING CFD METHOD

This article focuses on the aerodynamic and acoustic characteristics of both an isolated propeller model and a propeller - boundary surface model. The study uses the Reynolds-averaged Navier-Stokes (RANS) method combined with Computational Fluid Dynamics techniques to analyze the flow field and wake flow behind the propeller and to determine its basic aerodynamic coefficients. The pressure on the surface of the propeller and boundary surface is used as input for the noise calculations. An acoustic analogy method, based on the Farassat 1A formulation derived from the Ffowcs Williams-Hawkings (FW-H) equation, is employed to calculate the propagation of noise from the surfaces of the propeller and boundary surface to designated positions (microphones). The research results lead to some significant conclusions drawn by the authors.

Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review.

Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research.

Aeroacoustic Analysis of Rotor in Forward Flight Considering Blade Elastic Deformation

Abstract A rotor aeroacoustic calculation model of the rotor in forward flight based on CAMRAD II and FW-H equation was established, which can involve blade elastic deformation. CAMRAD II was used to calculate the actual motion of the blade and the rotor’s unsteady aerodynamic load based on the elastic blade model. The blade dynamics module in the noise calculation program was replaced to consider the blade elastic deformation in forward flight based on the FW-H equation. The forward flight noise characteristics of a full scale rotor were researched. The research shows that the rotor has obvious torsion and flap elastic deformation. The blade elastic deformation has little effect on the directivity of noise in forward flight. In the main noise propagation direction, blade deformation affects the loading noise, resulting in a maximum variation of 3.0dB or more in total noise. In noise calculation, the accuracy of noise prediction can be improved by matching the position of the real blade tip.

LDH-ViT: Fine-grained visual classification through local concealment and feature selection

Many methods based on Vision Transformer (ViT) have been proposed and applied in fine-grained visual classification (FGVC). It is of critical importance to improve the recognition accuracy and generalization ability of computer vision systems. However, the ViT model faces the challenges of increasing the amount of noise calculation, difficulty dealing with small targets with complex, diverse, and subtle characteristics in the images of the dataset, insufficient extraction of fine-grained information, and the impact of a few information patches on accuracy. To solve these problems an LDH-ViT model, which includes three new components. The LPC module randomly overshadows some of the small blocks separated from the ViT by a preset ratio. Subsequently, the local features of these new small blocks are calculated through training, aiming to reduce the influence of noise on the calculation process and further strengthen the difference between the images. The DFS module innovatively introduces a similarity selection layer, which aims to accurately identify and screen tokens with richer target information, thereby optimizing the information processing capability of the model. At the same time, the HMO module successfully constructs a new loss function based on the above improvements through clever fusion and optimization strategy. Comprehensive experiments on four widely used data sets show that LDH-ViT can achieve competitive performance.

A stereological study: Volume estimation in the cerebellum of Norduz sheep

In this research, it was aimed to investigate the cerebellum volume values of Norduz sheep raised within the borders of Gurpinar district of Van province. For this purpose, 6 male and 6 female Norduz sheep heads were selected as materials. The brains were dissected and kept in formaldehyde for a week. Cerebellums were separated from the brain hemispheriums. For better fixation, the cerebellums were kept in formaldehyde again for a week. Tissues obtained by sequential random sampling were included in tissue tracking. Then each tissue was embedded in paraffin. An average of 10-12 sections with a thickness of 5µm were obtained from the tissue cassettes obtained by a Rotary microtome (Leica RM, 2135, Nussloch Germany). Sections stained with hematoxylin and eosin were photographed with an x4 objective. From these photographs, total cerebellum, medulla and cortex volumes, as well as vermis volume, were calculated using the Shtereom I program using the Cavalieri Principle. The results were evaluated statistically with the Mann-Whitney U test. No statistical difference was detected in terms of male and female cerebellum volume values, Coefficient of Error (CE) and Noise calculations (p>0.05). However, in the evaluation between genders, it was determined that the only difference was seen in the medulla section of the hemispherium cerebelli sinister (p<0.05). Keywords: Cavalieri Principle; cerebellum; Norduz sheep; stereology; volume.

Analisis ergonomi lingkungan kerja fisik pada karyawan bagian laboratorium produksi

This research aims to analyze the impact of the physical work environment on employee performance at company X. An optimal physical work environment is identified as a key factor in increasing employee productivity and satisfaction. Through a quantitative approach, data is collected through employee surveys and physical work environment observations. An in-depth discussion of the implications of the findings for improving the physical work environment and company policies will be presented. This research is expected to make an important contribution to understanding the role of the physical work environment in improving employee performance, as well as providing a basis for companies to develop appropriate improvement strategies. The conclusion highlights the urgency of paying attention to the physical work environment as an investment to achieve optimal performance and employee satisfaction at company . These results show a figure of 71.2 dBA in noise calculations and 13.84 or 14 light points in lighting calculations, all of which indicate that the room is ergonomic enough for employees.

Analysis and measurement of magnetic noise for tesla shielding based on superconducting coils applied to SERF magnetometer

Tesla Shielding (TS) is closed superconducting coils composed of superconducting tape, designed to resist changing magnetic fields, thereby achieving magnetic shielding. TS, optically transparent, is suitable for integration with spin exchange relaxation-Free (SERF) magnetometers, thereby improving the sensitivity of SERF magnetometers. However, no prior research has been conducted on the magnetic noise of TS. Noise source identification was conducted on the superconducting tapes used in the TS. We modeled the magnetic noise of superconducting coils, analyzed the the relationship between geometric parameters and magnetic noise of coils, and proposed methods to suppress magnetic noise. Finally, we established a measurement system to measure the magnetic noise of superconducting coils. The results confirm the feasibility of the magnetic noise calculation model and the effectiveness of the methods for suppressing magnetic noise. This study can guide the design of TS, which is important for improving the sensitivity of SERF magnetometers.

Fault diagnosis of planetary gearboxes under small and imbalanced samples based on enhanced Siamese network with improved downsampling module

Due to the limitations of the operating conditions and equipment status, in practice, the normal data for planetary gearboxes are often sufficient, but the fault data are scarce and difficult to obtain, causing the fault diagnosis to face not only an imbalance problem but also a small sample problem. It leads to serious misdiagnosis and poor generalizability. To overcome above challenges, an enhanced Siamese network with improved downsampling module is proposed to reduce the negative impact of small and imbalanced datasets on fault diagnosis. Firstly, the Siamese network is combined with data enhancement to adaptively increase the fault training data with different small sample degrees. It can make the number of training data of each class get rid of small sample, while avoiding the excessive use of scarce fault data causing additional overfitting, so as to improve the generalization of the model. Among them, the data enhancement adopts the extreme noise expansion method proposed in this work, which can quickly generate samples that meet the requirements and help to improve the performance of the model in noisy environments. Secondly, adding the improved downsampling module to the Siamese network. The improved downsampling module introduces density-based spatial clustering of applications with noise (DBSCAN) and distribution ratio calculation, which can consider the distribution range and density of data when selecting. It can not only balance the training data, but also avoid serious information loss, and then reduce the probability of misdiagnosis. Finally, using six imbalanced planetary gearbox datasets with different small sample degrees for verification. The experimental results show that the proposed method can efficiently increase and balance the training data, which greatly improves the accuracy of fault diagnosis under the condition of small and imbalanced samples, especially when the small sample degree is very serious, the accuracy is improved by 57.76% on average.

SICALC - A new tool for aircraft noise calculations

This paper investigates how aircraft noise calculations can be made available for everyone. Traditionally, tools for aircraft noise calculations have been characterized by high complexity and numerous variables that users must consider. This complexity has necessitated expert competence to conduct calculations, limiting the accessibility of these calculations. SICALC (SINTEF Noise Calculator) is a new web-application tool that aims to challenge this practice and make noise calculation available to everyone while ensuring high-quality, reliable, uniform, and error-free results. The paper will discuss how the aircraft noise calculation method, NORTIM (the Norwegian Topography Integrated Model), has incorporated new technology and design principles into SICALC. It will also address the various challenges associated with this development.

Retro-diffraction - importance for the calculation of road traffic noise

In geometric acoustics, "retro-diffraction" describes the loss of energy when reflected at the upper edges of noise screens. By bending the sound beam against the direction of propagation under consideration, reflected energy of the mirror sound source is reduced by up to 5 dB in addition to the absorption. This effect becomes particularly effective if the sound beam is blocked by a noise screen in the direction of propagation under consideration, meaning that diffraction also occurs in this direction. Sound attenuation by retro-diffraction can be found in the French standard NF S 31-133, an alternative method to ISO 9613-2 for calculating sound propagation outdoors. It was incorporated into the French noise forecasting procedure NMPB in 2008. We also take it into account by using it in the procedure for calculating environmental noise (European: CNOSSOS; German: BUB). This paper attempts to determine the impact of considering retro-diffraction in sound propagation. First, the equations from ISO 9613-2 and BUB regarding retro diffraction are compared in a simple geometric model. The level differences calculated in commercial sound propagation software are compared with those from measurements on a 1:20 scale model. An estimate of the relevance of retro-diffraction in calculating sound propagation is given.

An efficient numerical model for the sound radiation from a supported rail

In this work, the sound radiation of a supported rail is investigated using a numerical 2.5D Finite Element model that is coupled with a 2.5D Boundary Element model. The vibration of the track is modelled by coupling the infinite rail to an equivalent continuous double-layer support and is used as input for calculating the consequent sound radiation. An interpolation method that allows for a quick solution of the boundary element calculations is proposed and validated by comparison with an analytical solution, showing differences less than 0.1 dB. The assembled model is used for calculating the sound radiation from the rail in terms of sound power per unit squared force applied to the rail head in vertical and lateral directions for three different rail configurations. The transfer functions obtained can be used in rolling noise calculations. The proposed interpolation method allows calculations that are more than 100 times faster than the regular procedure for the case considered.

Evaluation of railway noise calculation models using CNOSSOS-EU considering the effect of rail roughness

Railway noise assessment is an important tool in decision-making for urban planning, investment in transportation infrastructure and implementation of noise reduction strategies. Currently, the procedure is based on CNOSSOS-EU (Common Noise Assessment Methods in Europe), which was developed in accordance with European Directive 2002/49/EC. This method takes into account a variety of factors impacting rail noise levels, such as vehicle characteristics and track features. The purpose of this study was to investigate the influence of rail roughness on generated railway noise and to evaluate the accuracy of calculation models using CNOSSOS-EU. The study involved in-situ railway noise measurements at three different locations near the city of Zagreb, Croatia, and measuring rail roughness at each location. In order to eliminate the influence of other factors, the rail track structures at the measurement locations were similar, and an identical train configuration was used for the study. Finally, a comparison was made between calculation models based on default roughness values and models including values obtained from in-situ measurements. This approach enabled an assessment of the variations in CNOSSOS-EU calculation models taking into account actual in-situ rail roughness measurements.

An efficient predicting approach for blade frequency line-spectrum noise of marine centrifugal pumps

The paper introduces an innovative and efficient calculation method for the spectral flow noise of the pump system based on the spatial distribution dipole, which predicts the blade frequency radiation noise at the pipe flange of the pump system under different operating conditions. First, the unsteady flow simulation of the centrifugal pump is calculated using computational fluid dynamics (CFD). Then, the pressure on each segmented blade surface is decomposed into lift and drag forces. After that, each segment is decomposed into several dipole point sources based on the blade noise theory. Finally, the simplified dipole point sources are considered sound sources, and the blade frequency line spectrum noise at the pipe flange of the pump system is predicted using acoustic-structure coupling. The results indicate that the simplified method provides high prediction accuracy while significantly improving the computational efficiency of blade frequency line spectrum noise calculation for centrifugal pumps.

Handling of porous road surfaces in traffic noise calculations with Nord2000

Using porous road surfaces can be an alternative to more traditional noise reduction measures. Two factors contribute to the fact that road noise can get lower than with a conventional dense road surface: the rolling noise emission decreases, and the sound-absorbing road surface can further reduce the level. In a traffic noise calculation with Nord2000, the influence of the road surface on the sound emission is specified using road surface corrections while the acoustic surface impedance of the road surface determines the ground attenuation. However, due to measurement technical reasons, porous road surface corrections will include some (undesirable) ground attenuation, leading to that the rolling noise emission might be underestimated. Another problem is that the impedance model in Nord2000 (Delany & Bazley) does not give correct results for porous road surfaces. These complications have been investigated with Nord2000 calculations using a program code extended to also include an impedance model capable of handling porous road surfaces (Hamet et al). The results have been used to formulate official Swedish recommendations on how porous road surfaces can be handled in traffic noise investigations with Nord2000.

Improvement of noise calculation method considering aerodynamic noise condition during aircraft landing

Recently, while aircraft engine noise has become quieter, aerodynamic noise such as airframe noise, gear, and flaps have become relatively louder. In addition, the WHO environmental noise guidelines for the European region require consideration of small noise effects, and it has become necessary to increase the validity of calculations at distant airports, where aerodynamic noise fluctuations are large. Therefore, Nakazawa et al. reported a method to improve the validity of noise prediction for distant airports by correcting the existing noise calculation method to take aerodynamic noise into account. However, the predicted results deviated to a smaller extent than the measured results, indicating that the correction method needs to be improved. This method was improved, and using the results of highly accurate microphone array measurements with 195 microphones, NPD data for correction was prepared from aircraft noise by component using J-FRAIN, taking aerodynamic noise

The innovated national noise monitoring network in The Netherlands

Over ten years ago, the National Institute for Public Health and the Environment started monitoring noise emissions from major roads and railways in The Netherlands. Today, this monitoring program is still going strong. The measured data is used to validate the yearly reported noise production levels calculated by the Dutch road and railway authorities, to monitor trends in noise production, and to check the validity of the Dutch noise calculation method. Measurements in the entire network are performed at an altitude of four meters close to fifty meters from the major road or railway in free field as these are the requirements for the reported calculated levels. The network therefore, has to operate stand-alone, resulting in challenges in terms of power supply, datastorage and communication. Ten years ago, we started with a battery-powered network of simple and cost-effective dataloggers. Recently, we made innovations by transitioning to a solar-powered network of modern sound level meters with remote data communication. In this presentation I will give a brief history of this monitoring network, how it developed, and show you the possibilities of the present-day innovated network.

Sources for railway community noise modeling

For rail traffic, the wheel-rail interaction is one of the most important sources of noise, and is included in different ways in the noise calculation methods being used in Sweden today. However, if the rolling stock exhibit other noise sources it is not clear how they are handled by the different calculation methods. Recent measurements in Sweden of the newly refurbished 'X2' passenger trains indicate that cooling fan exhausts mounted high up on the driving unit radiate noise at levels corresponding to the wheel-rail noise at speeds of 200 km/h. The NMT96 calculation method currently used in Sweden represents the whole train as one line source per octave band, each placed at different heights. The newer Nord 2000 method, applies three sources at low heights for rolling noise and allows additional sources but without defining how to accommodate them. The Cnossos-EU method puts all potential exhaust and fan noise at the higher of two sources, at 4 m above the rail. None of the models define how to apply a source to just the locomotive as sound power is given per meter train or per rolling axis. The impact on noise exposure and mitigation is discussed in this paper.