Noise Path Research Articles

Importance of Vehicle Body Elements and Rear Axle Elements for Describing Road Booming Noise

For investigating influences of vehicle components on the acoustic comfort at low frequencies, e.g., the booming noise behavior of a vehicle, building a whole car simulation model is useful. To reduce the model’s complexity and to save resources in the validation process, we first identify relevant components before building the model. Based on previous studies, we focus on the vehicle’s body and the rear axle. In this paper, we analyze which axle and body elements are crucial for describing road booming noise. For this purpose, we use impact measurements to examine noise transfer functions of the body and a vibro-acoustical modal analysis to identify coupled modes between the body’s structure and the interior cavity. For investigating relevant force paths from the rear axle to the body, we used a chassis test bench. We identify the main transmission paths of road booming noise and highlight which axle and body components have an influence on them. Mainly the rear axle in its upright direction in combination with a rigid body movement of the rear tailgate coupled with the first longitudinal mode of the airborne cavity causes road booming noise. Furthermore, the rear axle steering, the active roll stabilization and the trim elements of the vehicle’s body are essential to describe road booming noise. The results can be used to set priorities in the validation of individual axle and body components for future simulation models. We found that the ventilation openings, the front seats, the headliner, and the cockpit of a vehicle have little influence on its noise transfer functions from the rear axle connection points to the driver’s ear between 20 and 60 Hz.

EMC Modeling and Conducted EMI Analysis for a Pulsed Power Generator System Including an AC–DC–DC Power Supply

High-voltage (HV) pulsed power generators are very important in plasma generation in corona discharge reactors. With the advent of new fast switches technologies such as silicon carbide (SiC) and gallium nitride (GaN), electromagnetic interference (EMI) noise in such systems are very challenging. In this article, electromagnetic compatibility (EMC) modeling and conducted EMI analysis for a pulse generator including an ac-dc-dc power supply are developed. Moreover, the common mode (CM) EMI noise propagation through the system is discussed and the noise sources and effect of each component on the noise flowing are analyzed. The ac-dc-dc power supply role is also investigated and since there is an isolation stage in the system, the effect of high-frequency (HF) transformers that provide a flowing path for noise is also studied. In addition, the CM impedance of different parts of the system as well as the noise voltage are discussed by regarding different values for parasitic parameters of the system. As the system noise level could not meet IEC61800-3 standard, EMI attenuation techniques were applied to the system. By using balance technique and adding filtering inductor as a decoupling inductance, the EMI noise is reduced. Furthermore, an EMI filter optimized and designed for the power supply system that could reduce the EMI noise level. However, by using some EMI reduction techniques that are explained in this article, the size of the required EMI filter is reduced. In this article, EMC modeling, conducted EMI analysis, and EMI reduction techniques led to higher performance and efficiency and lower size of EMI filter that reduced the overall size of the system.

An Optimization Method of Carrier Suppression for UHF RFID

The carrier leakage is the key factor that limits the performance of ultra-high frequency radio identification (UHF RFID) reader in high-power transmission mode. The relationship between phase noise suppression and path delay of the carrier leakage is discussed in this work. It is indicated that the suppression degree of the carrier leakage varies periodically with the carrier’s transmission path delay. A novel suppression method of the carrier leakage by adjusting antenna feeder’s length is proposed. The experimental results are provided to verify the feasibility and correctness of the method.

Implementation of a microphone array for improved noise path estimation in a feed-forward active noise control system

Active noise control (ANC) systems detect incoming sound and generate an anti-noise signal to attenuate it through destructive interference. ANC systems are generally limited to low-frequency sounds because the sensors and actuators are close together, leaving insufficient time to react to high-frequency or impulsive sounds. To compensate, common applications, such as noise-cancelling headphones, rely on complete ear coverings to block out higher-frequency sound indiscriminately, potentially hindering communication and situational awareness. The present work proposes to use an external array of microphones surrounding the user to increase the distance between the sensors and the user to afford more time to generate anti-noise signals and provide better path estimation. Using time delay of arrival (TDOA), the array tracks the locations of the user and the noise sources in real-time. The ANC system uses a feed-forward Filtered-x Least Mean Squared (FxLMS) algorithm that adjusts the weights of the controller based on the TDOA path estimation instead of adapting the filters with an error microphone and feedback loop. Simulations of the proposed system and feedback FxLMS path estimation were conducted in MATLAB. Compared to the feedback FxLMS algorithm, the TDOA system yielded 11 ± 1 dB less root-mean-square error in the generated anti-noise signals.

A Novel Deconvolution Cascaded Variational Mode Decomposition for Weak Bearing Fault Detection With Unknown Signal Transmission Path

Rolling element bearing is one of the most widely used component in mechanical equipment, whose reliability requirements are also increasing. In complex working conditions, the measured signals often contain so strong noisy interferences that the weak bearing fault features are difficult to be detected. Variational mode decomposition (VMD) is a widely used method for bearing fault features extraction. However, it also encountered some problems when dealing with weak fault signals, especially the number determination of decomposition modes, the influence of strong noise and unknown transmission path. In order to solve these problems, a novel deconvolution cascaded variational mode decomposition is proposed for weak bearing fault detection in this article. Considering the influence of transmission path and strong noise, a monitored signal is enhanced by compensation transfer function and optimized resonance component to reduce the impact of noise. Firstly, to compensate the transfer function of a complex unknown transmission path, a deconvolution method with multi-point kurtosis is used, which adjusts the filter adaptively to enhance the periodic impact component in the signal. Then, to determine the decomposition modes number and furtherly remove interferences noise, a cascaded variational mode decomposition is proposed for multi-layer noise suppression. Subsequently, a standardized square envelope spectrum is employed to detect fault characteristics of the resonant mode. Experiments verified the effectiveness of the proposed method, and comparisons show that the envelope factor is increased from 1.0762 to 34.8781, which mean that the fault signal is enhanced by the proposed method.

Noise model considering electrical feed-through under force rebalance closed-loop detection of MEMS gyroscope

This study analyses the transfer path of electrical feed-through noise in the electromechanical amplitude modulation detection circuit of a micro-electro-mechanical system vibrating gyroscope. By considering the feed-through, circuit and mechanical thermal noises, a new noise model in the force-to-rebalance closed-loop detection is constructed, and the expression of the noise-equivalent rotation rate spectrum is given. In addition, the influences of factors such as circuit gain, feedback coefficient and frequency split on the contribution of noise are analysed. The analysis shows that the back-end injection noise is the main factor affecting angle random walk (ARW) for high Q-value gyroscopes. Through actual measurements, it was found that the feed-through noise at the carrier frequency of the feedback circuit was the main source of the back-end noise. After noise optimization, the ARW of the detection output decreased from 0.148 to 0.017 , which was an improvement of about 8.7 times.

An investigation of the sound transmission loss for elastomeric vehicle door seals

The reduction of noise in vehicle body components is one of the main themes of the acoustics profession for vehicles. At high vehicle cruising speeds, the predominant contributor to wind noise occurs via the sealing system. Accordingly, understanding the sound transmission loss (STL) through a vehicle’s sealing system is an essential engineering context for reducing interior wind noise levels. The STL through a sealing system is affected by the material, cross-section design of the profiles, overall design of the sealing system and the dynamics of the system. In this study, a brief method is described to explore the acoustic properties of vehicle door seals. Material characterization is performed both for hyperelastic and viscoelastic regions and realized using mechanical tests. The method described for studying the STL covers an analytical approach, numerical analysis, and, finally, experimental validations for several door seals, which form a major part of the sealing system located around a passenger door (closing all direct noise paths and attenuating noise from the body). Finally, the effects of fundamental parameters on the sound transmission properties are presented.

Small Changes in Vehicle Suspension Layouts Could Reduce Interior Road Noise

Inside the passenger cabin of modern cars, lower noise levels from quieter engines make road noise more dominant. The main transfer path for road noise below 300 Hz into the car is the suspension. Suspension layouts are mainly determined by driving dynamics, but their influence on road noise is not in focus. Layout design changes for driving dynamics in the early development phase require the modification of structural dynamics Finite Element (FE) models used to predict interior acoustics. This manual modification makes acoustical effects from layout design changes difficult to predict. In the following article, we present a method to adapt suspension FE models automatically to suspension layout changes. This allows an automatic optimization of the suspension layout regarding road noise. As an example, a rear axle suspension layout is modified to decrease road noise between 60 and 90 Hz by moving the connection point between the track rod and the knuckle.

Quantum Propagator Derivation for the Ring of Four Harmonically Coupled Oscillators

The ring model of the coupled oscillator has enormously studied from the perspective of quantum mechanics. The research efforts on this system contribute to fully grasp the concepts of energy transport, dissipation, among others, in mesoscopic and condensed matter systems. In this research, the dynamics of the quantum propagator for the ring of oscillators was analyzed anew. White noise analysis was applied to derive the quantum mechanical propagator for a ring of four harmonically coupled oscillators. The process was done after performing four successive coordinate transformations obtaining four separated Lagrangian of a one-dimensional harmonic oscillator. Then, the individual propagator was evaluated via white noise path integration where the full propagator is expressed as the product of the individual propagators. In particular, the frequencies of the first two propagators correspond to degenerate normal mode frequencies, while the other two correspond to non-degenerate normal mode frequencies. The full propagator was expressed in its symmetric form to extract the energy spectrum and the wave function.

Analytical representation of Gaussian processes in the A−T plane

Closed-form expressions, parametrized by the Hurst exponent H and the length n of a time series, are derived for paths of fractional Brownian motion (fBm) and fractional Gaussian noise (fGn) in the A-T plane, composed of the fraction of turning points T and the Abbe value A. The exact formula for A_{fBm} is expressed via Riemann ζ and Hurwitz ζ functions. A very accurate approximation, yielding a simple exponential form, is obtained. Finite-size effects, introduced by the deviation of fGn's variance from unity, and asymptotic cases are discussed. Expressions for T for fBm, fGn, and differentiated fGn are also presented. The same methodology, valid for any Gaussian process, is applied to autoregressive moving average processes, for which regions of availability of the A-T plane are derived and given in analytic form. Locations in the A-T plane of some real-world examples as well as generated data are discussed for illustration.

Nano Boyutlu Vücut Merkezli Kablosuz Ağların Alveolar Alanları ve İnsan Dokuları için Numerik Analizi

This paper investigates the propagation of Terahertz (THz) electromagnetic waves inside the human body and discusses a model of the system performance of Nanoscale Body-Centric Wireless Networks inside the alveolar spaces and human tissues. THz band wireless communication enables new applications especially in nanoscale wireless communication. The model developed in this paper calculates the total absorption loss, path loss and capacity properties of EM waves propagating through the Alveolar Spaces and Human Tissues in nanoscale environment for THz band wireless communication. Based on the modeling of noise level and path losses, the channel capacity is calculated. The results show that Wireless Nanosensor Networks (WNSNs) can communicate through the human body. According to the numerical analysis of the model several transmission windows which are ω1 = [0.01 THz – 0.5 THz], ω2 = [0.58 THz – 0.74 THz] and ω3 = [0.77 THz – 0.96 THz] have been found for Nanoscale Body-Centric Wireless Networks. The longest and lowest transmission window which is in the range of 0.01 THz – 0.5 THz values have been analyzed for blood, plasma, RCBs and water to design universal nanonode for Nanoscale Body-Centric Wireless Networks at gases in lungs and blood.

A CM Filter Configuration for Grid-Tied Voltage Source Converters

Common mode (CM) filters play a crucial role in determining adherence to conducted emissions (CE) standards for grid-tied voltage source converters. Design and implementation of such filters can be challenging since they depend on several factors like identification of CM noise paths, fidelity of passive components and discerning the frequency and amplitude of CM noise sources. In this article, a CM filter has been proposed, which uses passive components along with the converter's heat sink as a circulating return path for the CM currents. Based on the presented CM circuit models with the proposed filter, a detailed design process has been delineated for selecting the passive components required to realize the CM filter. Additionally, the heat-sink potential has been shown to be touch safe during both ideal and nonideal grid conditions with the proposed CM filter. CE spectral results measured using a commercially procured line impedance stabilization network and captured time domain converter operational wave forms for a 2-level, 3π grid-tied voltage source converter validate the functionality and effectiveness of the presented design.

ABOUT THE COMMUNITY NOISE PROBLEM OF THE LIGHT PROPELLER AIRCRAFT

A light aircraft community noise problem was considered. Basic aircraft noise sources were described. A model was presented to evaluate engine-propeller aircraft power plant noise that may be used while estimating both light aircraft community noise and flight paths providing aircraft inaudibility in the housing system area adjacent to an airfield. An effective engineering analysis agreement of experimental and design power plant noise data has been given. Major light aircraft communication noise reduction methods have been considered. The principal future investigation directions were stated to provide scientific-and-engineering experience in developing present-day low-noise light aircraft has been developed.

Investigation on cutoff frequency and radial dependence of the sound field inelastic fluid-filled pipelines

Elastic fluid-filled pipeline system has been widely used in both life and military. It is of great significance for vibration and noise reduction of underwater vehicles to investigate the acoustic propagation characteristics of elastic fluid-filled pipeline system. The propagation path of low frequency noise in the pipeline is related to the radial dependence of the sound field in the pipeline. In this paper, the frequencies of normal waves in an elastic fluid-filled pipeline were calculated, and the axial and radial dependences of sound fields were analyzed. An experimental system for investigating acoustic propagation in a fluid-filled PE pipeline was constructed and verified the theoretical results. The cut-off frequencies of the normal waves and the radial dependence of the sound in the pipeline were carefully investigated. The results show that there is a sound cut-off phenomenon in the elastic fluid-filled pipeline; the radial dependence of the sound field in the pipeline conforms to the Bessel function law.

Parametric System Engineering Analysis of Capability-Based Small Satellite Missions

To achieve appropriate link budget and system engineering analyses of capability-based small satellites missions, an objective assessment and computation of the component-, subsystem-, and system-levels parameters requirements must be carried out. This paper presents the measurement-derived parametric models for the system engineering analysis of communication, meteorology, planetary, and other small satellite programs with recourse to the initial mission, conceptual design, and postmission objectives. Mass and power margins are the critical resources under investigation besides the link contingencies and operational times. The case study spacecraft systems engineering analyses indicate a transmit power for data transmission uplink and downlink of at least 33 dBm for the generic communication, meteorology, and planetary missions applications. The presented parametric models also reveal a signal-to-noise ratio of at least 16 dB per radio communication link for worst case noise floor and path loss. For a 30-W power utilization, a two-power communication-overpower mode mission operates for an extra 8.3 min compared with a three-power payload-overpower mode mission. This holds a great promise for the development of adaptive subsystems for reconfigurable multiband, and multistandard transponders for multipurpose missions and postmission applications.

Simulation and Analysis of Road Traffic Noise among Urban Buildings Using Spatial Subdivision-Based Beam Tracing Method

In order to realize the simulation and evaluation of road traffic noise among urban buildings, a spatial subdivision-based beam-tracing method is proposed in this study. First, the road traffic source is divided into sets of point sources and described with the help of vehicle emission model. Next, for each pair of source and receiver, spatial subdivision-based beam-tracing method is used in noise paths generation. At last, noise distribution can be got by noise calculation of all receivers considering the complex transmission among urban buildings. A measurement experiment with a point source is carried out to validate the accuracy of the method; the 0.8 m height and 2.5-m height average errors are about 0.9 dB and 1.2 dB, respectively. Moreover, traffic noise analysis under different building layouts and heights are presented by case applications and conclusions can be reached: (1) Different patterns result in different noise distributions and patterns designed as self-protective can lead to an obvious noise abatement for rear buildings. Noise differences between the front and rear buildings are about 7–12 dB with different patterns. (2) Noise value might not show a linear variation along with the height as shielding of different layers is various in reality.

Common-Mode Noise Modeling and Reduction for 1-MHz eGaN Multioutput DC–DC Converters

Enhancement-mode gallium nitride (eGaN) high-electron-mobility transistors (HEMTs) are promising to increase the switching frequency into multimegahertz for the high power density. However, it is a serious challenge to identify the equivalent lumped capacitances of megahertz multiwinding planar transformers for common-mode (CM) noise analysis to optimize the electromagnetic interference filters. The couple turn with its one-capacitor model is proposed to quantify the total CM noise current via the high-frequency transformer. With the modeled total CM noise current, the equivalent lumped interwinding capacitance model of the transformer can be derived conveniently and accurately. A complete CM noise path model is built for a GaN-based active clamp forward with a self-driven synchronous rectification multioutput converter. Then, a CM noise cancelation capacitance is applied and optimized to generate a reverse extraction current to cancel the CM noise current. Compared with other methods, the proposed modeling technique can build the equivalent lumped interwinding capacitance model of the multiwinding planar transformer in the printed circuit board layout stage before it is fabricated physically. The proposed model is verified by the experimental results with a 1-MHz GaN prototype with 100-V input, 5-V/6-A, and ±12-V/ 0.83-A outputs. The CM noise spectrum is well predicted. The CM noise is reduced by around 15 dB (a reduction of 12.6%) below 9 MHz.

Partial Coaxial Through-Silicon via for Suppressing the Substrate Noise in 3-Dimensional Integrated Circuit

In this paper, a novel through-silicon via (TSV) structure, named partial coaxial TSV (PC-TSV), is proposed to suppress TSV-induced substrate noise. In this structure, the via is surrounded by a benzocyclobutene (BCB) layer, and a grounded metal ring placed at one end. The BCB layer can effectively reduce the leakage of the signal to the substrate, and the metal ring provides a low impedance path for the substrate noise. An equivalent RLGC model of this structure is also established, and it is verified by simulated result from CST. Then, the performance of PC-TSV is compared with that of the traditional TSV, TSV with p+ layer, and TSV with p+ guard ring. Analysis results in frequency domain indicate PC-TSV has a larger $\vert \text{S}_{21}\vert $ and less near-end crosstalk than other three structures. Additionally, analysis results in time domain show that the substrate voltage noise of this structure is obviously reduced compared with the TSV with p+ layer and TSV with p+ guard ring. Also, a feasible process flow for this structure is given and it is simpler than that for traditional coaxial TSV.

Modeling and Analysis of TSV Noise Coupling Effects on RF LC-VCO and Shielding Structures in 3D IC

In this paper, we proposed through silicon via (TSV) to active circuit noise coupling model based on 3-dimensional transmission line matrix method and analyzed the noise coupling paths. When a TSV is located near the active circuit, the noise can easily travel through various coupling paths. With the proposed model, the noise coupling coefficient between TSV and the active circuit in a 3D IC can be estimated precisely. The cross-coupled differential LC-VCO was analyzed as the target active circuit because it is one of the main components in RF applications. With the suggested model, the noise coupling effects from the various coupling paths were compared, and the most critical noise coupling path was determined. We verified the accuracy of the proposed model with full 3D EM simulation results. Additionally, we proposed shielding structures using a guard ring and the ground TSVs for suppression of the noise coupling in 3D IC. The proposed noise suppression methods can reduce the TSV noise by blocking the noise paths to the active circuit. Various shielding structures were evaluated by comparing the different phase noise of LC-VCO to analyze the shielding effectiveness.

Converged Colored Noise Path Integral Molecular Dynamics Study of the Zundel Cation Down to Ultralow Temperatures at Coupled Cluster Accuracy.

For a long time, performing converged path integral simulations at ultralow but finite temperatures of a few Kelvin has been a nearly impossible task. However, recent developments in advanced colored noise thermostatting schemes for path integral simulations, namely, the Path Integral Generalized Langevin Equation Thermostat (PIGLET) and the Path Integral Quantum Thermal Bath (PIQTB), have been able to greatly reduce the computational cost of these simulations, thus making the ultralow temperature regime accessible in practice. In this work, we investigate the influence of these two thermostatting schemes on the description of hydrogen-bonded systems at temperatures down to a few Kelvin as encountered, for example, in helium nanodroplet isolation or tagging photodissociation spectroscopy experiments. For this purpose, we analyze the prototypical hydrogen bond in the Zundel cation (H5O2+) as a function of both oxygen-oxygen distance and temperature in order to elucidate how the anisotropic quantum delocalization and, thus, the shape of the shared proton adapts depending on the donor-acceptor distance. The underlying electronic structure of the Zundel cation is described in terms of Behler's Neural Network Potentials of essentially converged Coupled Cluster accuracy, CCSD(T*)-F12a/AVTZ. In addition, the performances of the PIQTB and PIGLET methods for energetic, structural, and quantum delocalization properties are assessed and directly compared. Overall, our results emphasize the validity and practical usefulness of these two modern thermostatting approaches for path integral simulations of hydrogen-bonded systems even at ultralow temperatures.