Noise Calculation Model Research Articles

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.

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.

Analysis and measurement of magnetic noise in multilayer magnetic shielding system combined with mu-metal and ferrite for atomic sensors

The multilayer magnetic shielding system is widely used in atomic sensors. However, for miniaturized atomic sensors with volume limitations, such as spin-exchange relaxation-free (SERF) gyroscopes, the remaining environmental magnetic interference and mu-metal magnetic noise will affect the sensitivity of atomic sensors. In this study, we establish a comprehensive magnetic noise calculation model for the magnetic shielding system of a SERF gyroscope, which considers the influence of the environmental magnetic noise on the magnetic shielding and the coupling effect between different layers. For suppressing magnetic noise of the magnetic shielding system, the property of different ferrites was measured and compared, then the particle swarm optimization is applied to design the magnetic shielding structure. Finally, the experimental device is established for measuring performances of the magnetic shielding system per and post optimization. By comparison, radial and axial magnetic noise post optimization are decreased by 37% and 22%, respectively.

Analysis of the calculation method and evaluation of the magnetic acceleration noise of space inertial sensor

Accurately calculating the magnetic acceleration noise is essential to designing the space inertial sensor and constructing its evaluation system. In view of the shortcomings of the magnetic acceleration noise calculation model, which considers the test mass (TM) as an ideal magnetic dipole rather than an entity, the Maxwell stress tensor method (MSTM) and virtual work principle method (VWPM), which consider the influence of the shape and size of the TM into account are adopted in this study. Through comparison, it is concluded that the non-uniformities of the internal magnetic field and magnetization intensity of the TM are the reasons for the calculation error of the model, and when the magnetic susceptibility is <1 × 10−2, the model can satisfy the requirement of the calculation accuracy. Finally, two specific signals of the near-interplanetary magnetic field and the magnetic field of a circuit board were measured in a magnetic shielding room (MSR), and the magnetic acceleration noises induced by the two magnetic environments were calculated. These can act as significant reference values for magnetic acceleration noise experiments in orbit and the layout of electronic devices in satellite engineering.

Modelling and analysis of electromagnetic force, vibration, and noise in permanent magnet synchronous motor for electric vehicles under different working conditions considering current harmonics

AbstractThe vibration and noise of the permanent magnet synchronous motor (PMSM) is mainly caused by its electromagnetic force. Harmonic currents affect the vibration, and noise performance of PMSM by influencing its electromagnetic force. The regularity of electromagnetic force, vibration, and noise characteristics of PMSM for electric vehicles (EVs) under different working conditions influenced by the harmonic currents is studied. Firstly, the analytical model of electromagnetic force under the action of a harmonic current is derived, and the influence of harmonic currents on the electromagnetic force of PMSM is summarised. Secondly, a multi‐physical field coupled vibration, and noise calculation model considering harmonic currents is established using the finite element method, and the vibration, and noise characteristics of PMSM under different operating conditions are analysed. The results show that the harmonic currents have different patterns of influence on the vibration, and noise of the PMSM due to the different advance angles and the saturation degree of the magnetic material under different working conditions. Finally, the validity of the theoretical analysis is verified by experiments, which has academic significance for vibration, and noise reduction of PMSMs for EVs.

Aircraft noise in situations with grazing sound incidence-Comparing different modeling approaches.

Current best-practice aircraft noise calculation models usually apply a so-called lateral attenuation term, i.e., an empirical formula to account for sound propagation phenomena in situations with grazing sound incidence. The recently developed aircraft noise model sonAIR features a physically based sound propagation core that claims to implicitly account for the phenomena condensed in this correction. The current study compares calculations for situations with grazing sound incidence of sonAIR and two best-practice models, AEDT and FLULA2, with measurements. The validation dataset includes on the one hand a large number of commercial aircraft during final approach and on the other hand departures of a jet fighter aircraft, with measurement distances up to 2.8 km. The comparisons show that a lateral attenuation term is justified for best-practice models, resulting in a better agreement with measurements. However, sonAIR yields better results than the two other models, with deviations on the order of only ±1 dB at all measurement locations. A further advantage of a physically based modeling approach, as used in sonAIR, is its ability to account for varying conditions affecting lateral attenuation, like systematic differences in the temperature stratification between day and night or ground cover other than grassland.

Additional noise reduction with diffracting elements on barriers using numerical and standard calculation methods

The noise reduction of a (low) barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. A so-called Whiswall or WHIStop deflects sound upwards for specific frequencies. Measurements for a 1.1 meter high Whiswall and for a 1.1m barrier are compared in a separate paper. The enhanced barrier effect is measured at a short distance behind the barrier, for several situations. In this paper these measurements are compared with the results of a numerical finite element model (FEM) to validate this model. Next, the noise reduction is calculated at long ranges, up to 600 meters, for different point-to-point scenarios representative for road and rail traffic. A numerical parabolic equation method (PE) is coupled to the FEM model and a representative downwind condition is taken into account. The results at longer distance are used to design an engineering method for the enhanced barrier effect that can be used in standard noise calculation models, such as the Dutch national calculation model (SRM2) or the ISO 9613-2 standard.

Noise Calculation Method for Deep Groove Ball Bearing With Considering Raceway Surface Waviness and Roller Size Error

Rolling bearing is a kind of important part of mechanical equipment, and the noise of the rolling bearing is also one of the important criteria for evaluating the quality of a rolling bearing. In the past, researches on rolling bearings are mainly on bearing vibration when people study the noise of bearings. Few studies have established rolling bearing’s noise model. In this paper, a mathematical model for calculating the inner ring’s axis center orbit and ball center’s trajectory of bearing is established based on the mechanics theory with considering raceway waviness and ball size error. Combined with the acoustics theory, a noise calculation model for deep grove ball bearing is established by taking the bearing inner ring and rolling balls as cylindrical sound source and spherical sound source respectively by using the single source compound method. The influences of waviness wave number, waviness amplitude, bearing speed, bearing load and ball size errors on bearing noise at a fixed measuring point are studied by numerical calculation. Results show that with the increase of the waviness wave number, the bearing SPL(Sound Pressure Level) will change with irregular way. With the increase of waviness amplitude, bearing speed, bearing load and ball size error band, the bearing SPL will increase.

Rapid engineering assessment method for acoustic design of metro trains

The low noise design must be embedded in every design phase of the train vehicles. The vehicle noise calculation models are established by taking full account of vehicle geometrical dimensions, measuring point location, noise sources, sound insulation and sound absorption. These models can (1) complete quantitative assessment of acoustic structures and noise sources of the vehicles to achieve the top-down quantitative control of acoustic index; (2) calculate interior noise and exterior noise under static conditions, running conditions, as well as tunnel environment conditions; (3) calculate and analyze noise limit values of main noise sources when the sound insulation of walls have been given, such as floor, side wall and gangway; and (4) calculate and analyze sound insulation limit values when the sound power of main noise sources have been given. The average differences between the A-weighted measured and predicted levels are less than 2 dB. The models show a very important guiding role for quantitative acoustics design of metro trains.

A methodology to control urban traffic noise under the constraint of environmental capacity: A case study of a double-decision optimization model

This paper presents a novel methodology to control urban traffic noise under the constraint of environmental capacity. Considering the upper limits of noise control zones as the major bottleneck to control the maximum traffic flow is a new idea. The urban road network traffic is the mutual or joint behavior of public self-selection and management decisions, so is a typical double decision optimization problem.The proposed methodology incorporates theoretically model specifications. Traffic noise calculation model and traffic assignment model for O–D matrix are integrated based on bi-level programming method which follows an iterated process to obtain the optimal solution. The upper level resolves the question of how to sustain the maximum traffic flow with noise capacity threshold in a feasible road network. The user equilibrium method is adopted in the lower layer to resolve the O–D traffic assignment.The methodology has been applied to study area of QingDao, China. In this illustrative case, the noise pollution level values of optimal solution could satisfy the urban environmental noise capacity constraints. Moreover, the optimal solution was intelligently adjusted rather than simply reducing the value below a certain threshold. The results indicate that the proposed methodology is feasible and effective, and it can provide a reference for a sustainable development and noise control management of the urban traffic.

A New CDS Structure for High Density FPA with Low Power

Being an essential part of infrared readout integrated circuit, correlated double sampling (CDS) circuits play important roles in both depressing reset noise and conditioning integration signals. To adapt applications for focal planes of large format and high density, a new structure of CDS circuit occupying small layout area is proposed, whose power dissipation has been optimized by using MOSFETs in operation of subthreshold region, which leads to 720 nW. Then the noise calculation model is established, based on which the noise analysis has been carried out by the approaches of transfer function and numerical simulations using SIMULINK and Verilog-A. The results are in good agreement, demonstrating the validity of the present noise calculation model. Thermal noise plays a dominant role in the long wave situation while 1/f noise is the majority in the medium wave situation. The total noise of long wave is smaller than medium wave, both of which increase with the integration capacitor and integration time increasing.

Road traffic noise mapping in Guangzhou using GIS and GPS

The primary objective of this study is to develop day and night road traffic noise maps for Guangzhou using Geographical Information Systems (GIS) and Global Positioning Systems (GPS). First, as speed-density relation is used to estimate the traffic volume from GPS data collected from floating cars. Meanwhile, the attributes of the roads and buildings are automatically exported from GIS. Second, a single vehicle noise emission model is combined with a noise propagation model to formulate a regional traffic noise calculation model that accounts for the traffic noise attenuation in an urban area. The algorithm is optimized by intelligently dividing the computational grids, filtering the traffic noise sources automatically and performing a quick index of the estimation objects. Finally, the day and night road traffic noise levels in Guangzhou are estimated to create two traffic noise maps. The accuracy of the developed algorithm is validated by conducting a traffic noise monitoring experiment in several districts of Guangzhou with different road types. The results show that the average error between the estimated and measured values is below 2.0dB.

A Model to Predict Sound Reflections from Cliffs

In the context of the Swiss railway noise calculation model sonRAlL a model to predict sound exposure level spectra for reflections from cliffs was developed and validated with measurements. It is an engineering model with low computational cost that is applicable to any type of sound sources. The scattered energy reflected from the cliffs is modelled by the superposition of secondary sources placed on the cliff surface. The only free parameter of the model, the scattering coefficient, was determined by measurements with detonations of 200 g TNT e q in the alpine part of Switzerland. Measurements yielded good agreement not only in situations with reflecting cliffs but also in the presence of large boulder fields.

Sound Propagation over Ballast Surfaces

Sound emission measurements of railway vehicles are usually performed with microphones close to the railway line. In case of double-track lines and vehicles on the distant track ground reflections develop mainly above the ballast bed. The uncertainty of estimated sound power based on microphone signals depends on the accuracy of considered propagation effects. It is found that ground reflection over ballast has to be understood as an extended-reaction process. With the application of a simple geometrical model for a ballast structure good agreement between measurement and calculation could be achieved. The model was validated for a large set of loudspeaker measurements conducted at the occasion of the development work of sonRAIL, the new Swiss railway noise calculation model.

Noise limits and noise levels along motorways in Europe

Environmental noise caused by traffic is one of the main local environmental problems in Europe. The National Road Authorities (NRA's), combined in the Conference of European Directors of Roads (CEDR), are aware of the environmental noise problem along their motorways. One of the main objectives of CEDR is to facilitate knowledge sharing on noise abatement issues among European NRA's. The CEDR noise group has made a comprehensive questionnaire survey on how the CEDR member states handle noise issues. The paper focuses on the part of the survey on noise limits and noise levels along motorways throughout Europe. It will deal with the: ‐ status of noise limits; ‐ noise indicators to express noise limits; ‐ noise limits (outdoor and indoor) for motorways; ‐ noise models to calculate noise levels. Due to the use of different noise indicators and different noise calculation models, the comparison of noise levels and noise limits along motorways in Europe is complicated to say the least. The only way to solve this problem is to have and to use a European noise model for road traffic based on the outcome of the HARMONOISE/IMAGINE projects.

On the Accuracy of Direct Noise Calculations Based on the Euler Model

The paper reviews a class of Direct Noise Calculation (DNC) models based on the compressible Euler equations and analyses their computational accuracy considering the combination of model completeness, scheme accuracy and stability to round off errors. It is shown that a form of the Nonlinear Disturbance Equations (NLDE) is sensitive to the round off errors. An NLDE formulation with Roe average matrix (NLDE/Roe) for minimizing the round off errors is proposed. (The NLDE/Roe is identical to Direct Numerical Simulation (DNS) at rather large solutions and converges to the Linearised Euler Equations (LEE) at the small solutions NLDE/Roe thus accurately treats the signals including both large and small scales of disturbances). A version of NLDE in the case of disturbance decomposition is given in the general form. While studying the DNC model efficiency, a new measure of the total model accuracy is introduced. It is proposed to test all the models and schemes available by comparing the output numerical result with the exact solution of the complete model, that is, with the Euler equations.

Geographical information system for traffic noise analysis and forecasting with the appearance of barriers

This paper describes a road traffic noise calculation and visualization package TNoiseGIS. It is implemented by utilizing the inbuilt database and spatial routines of a popular commercial Geographical Information System (GIS). The noise calculations can be made according to either of two alternative noise calculation models: the UK CORTN and US FHWA models. These models are applicable for calculating noise levels along highways with free flowing traffic. By applying the inbuilt spatial operations to the geographically located information, noise emission values can automatically be provided for any number of receptor points using either algorithm. The graphical user interface of the GIS simplifies the input of the attributes of the different receptor points and road links. Line and block barriers can be defined and applied with the interpolation technique for calculating traffic noise on receiver points along the back edge of barrier parallel to roadway. As a result, all noise levels behind the barrier can be efficiently estimated. In addition to the calculation of noise emission values for a specified set of receptor points, the variation in the noise levels along the highway can be visualized in the form of noise contours. Such contours provide a visual description of the soundscape and also information on the importance of different factors for soundscape quality. By changing traffic flow parameters such as the localization of planned roads, dwellings, and barriers with different size and location, TNoiseGIS functions as a road traffic noise prediction tool and a tool for planning environmentally friendly road and road traffic noise solutions. The noise calculations and visualization algorithms are implemented by means of scripts that will be made available at a lower cost and also user modifiable.

Comparison of Road Traffic Noise Calculation Models

The results of a round robin test on road-traffic noise calculation schemes are presented and analyzed for differences. On the basis of the information supplied, corrections were applied to make results more comparable. Every day situations, as simple as possible were presented, such as straight, asphalted roads with no reflections, ramps, curves or blocks. The spread in results is large, from 6 to 10 dB, with larger differences for the motorways and for the night situation. On closer examination of the calculation models the source models were seen to cause the largest differences. The conclusion is therefore that before comparing noise levels and standards between countries, one should be aware that large unexplainable differences result when the same situations are calculated with different methods. The differences vary between 6 and 10 dB(A), even after correction. This means that the differences when comparing official outcomes (according to the national standards) may be even larger. The need for combined effort to establish a common calculation method is obvious. From the data it seems impossible to prepare a translation between methods since the differences lack any trend.

On the modelling of the effect of ground terrain profile in environmental noise calculations

A simple model for the calculations of the attenuation of complex ground terrain profiles is developed. The model is based on the simple ground reflection and minimum diffraction path model developed by Lam [Lam, Y.W. & Roberts, S.C., J. Acoust. Soc. Am., 93(3) (1993) 1445-52]. The ground model is compared with existing environmental noise calculation models: the draft ISO model, the CONCAWE model, and ENM. It is found that the new ground model has the best overall performance and agrees well with measured data on a variety of ground terrain profiles and conditions. The measured data are taken from the existing literature and cover both short- and long-range propagation. Serious errors are also found in the draft ISO model and in ENM which cast doubts on their suitability as standard environmental noise calculation models.