Vibration Noise Research Articles

Experimental investigation of particle impact dampers: Vibration reduction and noise levels with varied particle numbers

Structural vibrations present significant challenges in engineering systems, and particle impact dampers (PIDs) have emerged as a promising solution for vibration control. This paper presents a comprehensive experimental investigation on the damping performance of PIDs with varying numbers of particles. The experimental setup involves subjecting a single-degree-of-freedom (SDOF) structure to base motion excitations. Frequency response analysis is conducted to assess the dynamic behavior of the primary system using different PID designs. PIDs with one mass, two masses, three masses and multiple particles are designed and analyzed using the same mass ratio. Additionally, time domain displacement responses of the top of the structure and the base are measured to capture the system's response characteristics. The frequency response analysis reveals the influence of different particle configurations on the system's response amplitude at various frequencies. Interestingly, the results show that a PID with multiple particles exhibits reduced damping performance due to excessive particle-particle collisions. These collisions decrease the energy of the particles, leading to lower velocity before impact. This highlights that the impact itself is the primary source of damping in PIDs, and any other phenomena, such as particle-particle collisions, directly affect the relative velocity before impact. The outcomes demonstrate that an optimal design of PID can reduce vibration amplitude by approximately 85 % with single mass, two masses, and three masses configurations. Conversely, the best-case scenario of PID with multiple particles provides a vibration amplitude reduction of 75 % compared to the absence of a damper. Furthermore, noise data is recorded for all cases, as noise generation is a significant concern associated with PIDs. The results indicate noise magnitudes of 62.5 dB, 70.60 dB, 73.24 dB and 78.64 dB for PIDs with single mass, two masses, three masses, and multiple particles, respectively. Overall, the relationship between the number of particles and damping performance provides valuable insights for optimizing PID designs and ensuring comfortable operation. The findings have broad implications for diverse engineering systems, leading to improved structural performance, reduced noise, and enhanced safety. This study could serve as the basis for several potential applications of PID in structural vibration control with enhanced performance and reduced noise.

Effect of epoxidation level on rheological properties of epoxidized natural rubber-based magnetorheological elastomer

Epoxidized natural rubbers (ENR)are potential to be an alternative of natural rubber as matrix of magnetorheological elastomers (MREs). These ENR-based MREs offer various advantages such as excellent mechanical properties and damping characteristics that are well-suited for applications in vibration control and noise reduction devices. However, there is a paucity information in regard to the effect of different epoxidation levels on rheological properties of MRE. Therefore, the main aim of this study is to explore the influence of epoxidation level on rheological properties of MRE using commercialized ENR corresponding to ENR 25 and ENR 50. ENR-based MREs were created by blending with carbonyl iron particles (CIPs) and other additives, followed by curing at 150 °C for 30 min. The study involved producing ten MRE samples with various weight percentages of CIP (0,10,30,50 and 70 wt%). The storage modulus of ENR 50 exhibited a significant increment from 0.73 MPa to 1.04 MPa as compared to ENR 25 which caused the storage modulus to increase from 0.77 to 0.88 MPa. This showed that ENR 50-based MRE are stiffer in comparison to ENR 25-based MRE. Initial loss modulus value for ENR 50 (0.098 MPa) was lower than that of ENR 25 (0.112 MPa), consequently less energy is dissipated to surrounding for ENR 50-based MRE compare ENR 25-based MRE. The loss factor that represents damping properties showed that ENR 50 reached higher values (0.120 MPa) compared to ENR 25 (0.106 MPa). The increasing of CIPs content from 0 to 70 wt% contributed to increasing of magnetorheological effect for both ENR-based MRE where ENR 25 produced slightly higher with increment of 1.88 % to 22.6 % than ENR 50-based MRE with increment of 2.47 % to 18.18 % due to rise of magnetic forces generated from interaction of magnetic moments in magnetic domains of each CIPs. The results and analysis indicate that different levels of epoxidation in ENR have a marginal impact on the rheological properties of ENR-based MREs.

Enhanced detection performance based on a differential ME sensor with strong suppression of vibration interference

Magnetoelectric (ME) sensors have enormous potential for detecting weak magnetic fields because of their high sensitivity, low power consumption, compact size and, low cost. However, inevitable vibration interference limits their application in practical environments, especially in the case of mobile platform mounting. Here, we propose a differential ME sensor, consisting of PZT macro-fiber composites (MFCs) and Metglas laminates. The differential ME sensor has two output terminals with weak mutual mechanical coupling and works in longitudinal vibration mode. MFC cores are polarized in parallel mode to guarantee their consistency of electric characteristics and reversed bias field is provided by attached magnets. Experimental results show that the differential-mode response amplitudes have a gain of −17.6 dB for low-frequency vibration at 2 Hz and ∼6.2 dB for an applied magnetic field at 3 Hz, in comparison with the single-ended mode. In addition, our proposed ME sensor also has a low inherent equivalent magnetic noise of 18.3 pT/√Hz at 1 Hz. Finally, a target detection experiment in the presence of heavy lab noise and strong vibration interference is conducted and the improved detection performance of the proposed differential ME sensor is proved.

Modified Arithmetic Optimization Algorithm (MAOA) based torque ripple minimization for a sensorless BLDC motor

ABSTRACT Permanent magnet brushless DC (PM BLDC) motor drives outperform the induction motor drives in terms of performance and improved efficiency. Recent advancements in power electronics technology have improved the application of BLDC drives in a variety of home applications. However, the BLDC motor drives suffer from torque ripple, which causes machine vibration, speed oscillations, and acoustic noise, limiting the application range. In this prelude, an optimization tuning algorithm, namely Modified Arithmetic Optimization Algorithm (MAOA) is suggested in this paper for torque ripple minimization in a sensorless BLDC drive. In this paper, the cuk converter topology with PAM scheme is proposed for the sensorless BLDC drive, and MAOA algorithm is used to improve the gain of the controller. A MATLAB Simulink model is used to validate the results of MAOA tuned BLDC drive.

Loaded tooth contact analysis for helical gears with surface waviness error

Meshing characteristics are crucial for the transmission performance of vibration noise and strength of gear systems. Gear transmission error has been acknowledged as a prominent excitation in vibration systems, but the surface waviness deviations that directly affect it in contact analysis are generally ignored. This study proposes a comprehensive model for quasi-static analysis of tooth surfaces with waviness error. The model reconstructs the actual tooth surface in reverse based on the gear Fourier measurement principle. Instead of solving the meshing equations to pre-assume contact position, the problem of normal contact between surfaces with deviations is solved by an innovative multiscale grid and a local iterative numerical algorithm. Combining the finite element numerical method and surface integral of the Boussinesq solution determines gear deformation and develops a loaded contact model. The validity of the model is verified through numerical examples. Furthermore, the proposed model is applied to discuss the tooth surfaces with different waviness amplitudes, frequencies, and distribution angles for the first time. It explains the interaction between local microscale and global scale introduced by waviness error on tooth surfaces and reveals the mechanism of the waviness error on meshing performance.

A factor analysis based automatic optimization method of vibration sensor points for ship acoustic reconstruction

To address the challenge associated with optimizing the number and positioning of accelerometer points in ship acoustic reconstruction, factor analysis is applied to the automatic optimization of accelerometer position in this work according to the source independence of ship’s underwater radiated noise. Based on the numerical simulation method that calculates the vibration noise response under specific operation conditions, the minimum number and the optimal position of the accelerometers can be obtained through the factor analysis and multi-parameter comprehensive evaluation method. The results of acoustic reconfiguration and testing are compared using one test cabin as a validation object to verify the effectiveness of the proposed method. The results show that the automatic optimization algorithm can improve the reconstruction accuracy concerning the uniform distribution method. The error is reduced from 15.46% (1.5 dB) to 8.35% (0.8 dB), and the correlation coefficient is improved from 0.86 to 0.89. The semi-automatic optimization method is slightly lower in terms of errors and correlation coefficients compared to the automatic optimization algorithm. After increasing the number of monitoring positions for automatic optimization, the acoustic reconstruction accuracy is further improved, while the average error is reduced to 7.37% (0.7 dB) and the correlation coefficient is improved from 0.89 to 0.92. The experimental results are proximate to the conclusions of the simulation calculation. Even under the circumstance of multi-factor noise interference, the correlation coefficient of multi-position automatic optimization can still reach 0.8, in comparison with the uniform distribution method, the error is reduced from 32.49% (3.4 dB) to 25.94% (2.6 dB). The proposed method effectively captures the dynamic characteristics of complex structures and their impact on underwater radiated noise, and the integration of factor analysis can prominently enhance the computational efficiency, thereby providing technical support for engineering applications to the ship acoustic reconstruction.

Chaotic band-gap modulation mechanism for nonlinear vibration isolation systems based on time-delay feedback control

Abstract Systems designed for nonlinear vibration isolation that incorporate chaotic states demonstrate superior capabilities in vibration attenuation, adeptly modulating the spectral constituents of vibrational noise. Yet, the challenge of eliciting low-amplitude chaotic dynamics and perpetuating these states across a diverse array of parameters remains formidable. This study proposes a pioneering strategy and technique for modulating the chaos band by incorporating a time-delayed feedback control mechanism within the framework of nonlinear vibration isolation systems.The investigation commences with an exhaustive analysis of the nonlinear dynamics, shedding light on the principles dictating the evolution of chaos. The study then advances to scrutinize the dynamics of systems with delays to elucidate the chaos-inducing processes engendered by feedback with temporal lags. Building upon the system’s responses, the chaotic performance and the effectiveness of the vibration isolation are crafted. Consequently, the time-delayed feedback control parameters are identified as pivotal design variables, which are then employed to dissect the control mechanisms influenced by the time-delayed feedback on the chaos band. Utilizing the delineated control mechanism, the nonlinear vibration isolation system is precipitously transitioned from a state of stable periodicity to one of chaos, fostering low-amplitude chaotic dynamics across an expansive parameter space, and in turn, resolving the previously stated challenge. Perhaps most significantly, the mechanism for attaining low-amplitude chaos introduced here paves the way for innovative methodologies in the active vibration isolation design of similar systems. Furthermore, it is anticipated to yield theoretical guidance for the manipulation of chaos bands and the formulation of active vibration isolation strategies within the domain of nonlinear vibration isolation systems.

Feasibility Assessment of Rapid Response EEG in the Identification of Nonconvulsive Seizures During Military Medical Air Transport.

Traumatic brain injury often requires neurologic care and specialized equipment, not often found downrange. Nonconvulsive seizures (NCSs) and nonconvulsive status epilepticus (NCSE) occur in up to 30% of patients with moderate or severe traumatic brain injury and is associated with a 39% morbidity and an 18% mortality. It remains difficult to identify at bedside because of the heterogeneous clinical manifestations. The primary diagnostic tool is an electroencephalogram (EEG) which is large, requires an external power source, and requires a specialized technician and neurologist to collect and interpret the data. Rapid response EEG (rr-EEG) is an FDA-approved device that is pocket sized and battery powered and uses a disposable 10-electrode headset. Prior studies have demonstrated the noninferiority of rr-EEG in the identification of NCSE and NCS as compared to conventional EEG in hospitals. An unanswered question is whether rr-EEG could be used in the identification of NCSE and NCS by medics. In conjunction with the Critical Care Air Transport (CCAT) team, a simulation was created and implemented on a CCAT training mission. The simulation team included a neurology resident, who oversaw the simulation, a pulmonary critical care fellow, an intensive care unit nurse, and a respiratory therapy. A survey was provided before and after the simulation. The team was expected to review the rr-EEG to make clinical decisions during ground transport, takeoff, and landing. The neurology resident monitored and recorded the team's ability to distinguish between NCS and a normal EEG. In between, the neurology resident monitored the quality of the EEG for potential interference and loss of quality. The CCAT team was able to efficiently set up the rr-EEG on a patient manikin, correctly identify visual EEG wave forms of a patient in NCS, and utilize the proprietary audio program of a simulated patient in NCS. The team reported that the device was easily set up in the environment, and the data were interpretable despite vibration, aircraft auditory and electrical noise, and the ergonomics of the aircraft medical section. This pilot study has validated a potentially revolutionary technology in medical transport. The rr-EEG technology is measurably user-friendly and will improve patient outcomes. This device and simulation can reduce time to an EEG by hours to days allowing for immediate treatment and intervention, which can significantly reduce morbidity and mortality.

Analysis of friction vibration characteristics of the end face of a T-slot sealing ring under thermal deformation

Aiming at the friction vibration problem caused by dry friction contact during the start-stop process of a dry gas sealing device, this paper takes the end face of a T-slot dry gas sealing ring as the research object and establishes a numerical calculation model of the end face of the T-slot sealing ring. The thermal coupling method is used to obtain the thermal deformation law of the seal ring end face. The transient dynamics analysis method was applied to study the frequency and vibration mode of the friction vibration instability of the seal ring end face under thermal deformation. A vibration test bench was set up for the friction ring, and the friction vibration signals of the test pieces were collected, and the characteristic frequencies were extracted. The results show that: After thermal deformation, the end face of the sealing ring changes from a parallel surface to an inward converging surface, and the friction system of the sealing ring will become unstable. When considering the influence of thermal deformation, there are more unstable frequencies and lower frequency values that are most prone to frictional vibration. As the thermal deformation of the sealing ring increases, the frictional vibration becomes greater. In areas where the characteristic frequency values of frictional vibration are concentrated during thermal deformation, the occurrence rate of frictional vibration noise is higher.

VibraSIG - Modeling railway structure-borne noise and vibrations and implementation in QGIS geographic information software

In the context of engineering studies for passenger rail line projects, a method for predicting vibration and structure-borne noise levels in buildings close to the line is needed on the scale of a town or territory. ACOUSTB has developed VibraSig, a method for calculating railway vibration and structure-borne noise, based on two numerical models (VibraFer, CSTB and MEFISSTO, CSTB). A numerical model in VibraFer is used to define a railway excitation source term. A numerical model in MEFISSTO is used to calculate the vibratory response of the tunnel and the ground up to the building on a cross-section. A statistical building response model is used to estimate structure-borne noise and floor vibration levels. Finally, the method for predicting vibration and structure-borne noise levels is extended to the entire project route, and the results are visualized for each building on a Geographic Information System (GIS).

Railway-induced vibration combined with railway noise - a systematic review with exposure-effect curves

The combined health impact of concurrent railway noise and railway vibration exposure is not yet well understood. This systematic review aimed to investigate the combined effects of vibration and concurrent noise. We converted the vibration metric to an equivalent noise level and calculated an overall noise level by energetically summing the equivalent and railway noise level. The combined health effect was determined by using published evidence-based exposure-effect formulas. Studies included in this systematic review predominately investigated annoyance and self-reported sleep disturbances; no studies on manifest diseases were identified. For the combined effects of vibration and noise on "total" annoyance, the results based on the pooled analysis of CargoVibes project are recommended as conservative approach. Our results based on epidemiological studies are corroborated by findings of laboratory studies. Converting railway vibration into equivalent noise levels in dB may offer a pragmatic approach to assess the combined health effects of railway noise and railway vibration exposure. Future studies should include cardiovascular and mental diseases in addition to vibration-induced annoyance and sleep disturbances. Furthermore, future studies should include in-depth investigations of the interaction between railway noise and railway vibration to allow for a more accurate assessment of the railway-induced burden of disease.

Annoyance caused by simultaneous exposure to noise and seat vibrations inside of a mini excavator: multimodal interaction and the effects of changes in low-frequency content of the sound signal

Drivers of commercial vehicles are exposed to noise and vibrations during their occupation. The signal characteristics of these exposures can lead to different degrees of annoyance perception, even below the legal daily exposure limits. In addition, simultaneous exposure to sound and vibration may lead to potential interaction effects between the two stimuli, influencing the total annoyance perception. Therefore, a perception experiment was designed to ask the participants about the perceived total annoyance caused by simultaneous noise and seat vibrations in commercial vehicles, presenting modified sound and seat vibrations, recorded inside of a mini-excavator. Multimodal interaction effects of noise and vibrations were investigated by changing the intensity of both stimuli. Furthermore, the influence of low-frequency signal components of the sound signal with and without simultaneous seat vibrations was investigated by specific changes in the sound spectrum.

Research on the effects of railway noise and biaxial vibration on calculation disturbances

This study conducted an evaluation experiment on simultaneous exposure to noise and two-axis vibration stimuli from railways, using noise stimuli from railways and two-axis vibration stimuli in the horizontal-vertical direction, and verified differences in evaluation of interference due to differences in noise and the direction of vibration. The experiment was conducted in a laboratory with a vibration exciter placed in a simple anechoic chamber, with the participation of 20 students. The stimuli presented utilized vibrations recorded indoors and sounds recorded outdoors. Both vertical and horizontal vibrations were presented in four levels, and the sound stimuli were presented at three levels: 50, 60, and 70 dB. The evaluation of annoyance and interference showed that under conditions of noise levels of 50 dB and 60 dB, discomfort and interference increased as the vertical vibration level increased with horizontal vibration levels (X: 2-6), confirming the combined effect of vertical vibration and noise. Even under conditions of a noise level of 70 dB, except for vibration conditions X: 2, Z: 2, and X: 6, Z: 6, the combined effect of vertical vibration and noise was confirmed.

Automotive powertrain electrification: system methodology to guarantee acoustic comfort

For the past few years, electrification has disrupted the automotive industry. Surprisingly, Noise Vibration and Harshness (NVH) became a major issue as it is located in high frequencies (1 to 5 kHz). The noise has 2 origins: the electromagnetic forces in the electric motor and the gear mesh forces in the reducer. The first part focuses on the methodology developed in collaboration with car-makers in order to integrate the powertrain in a satisfying way in the vehicle. First, this process is focused on the structure-borne noise. Attention is paid on rubber mounts and on their fixation points. Second, the airborne transfer may become an issue. Despite the acoustic power requirement provided, the final vehicle performance is not guaranteed. Examples will illustrate these important topics. The second part pays attention to the prediction of reducer noise. Automotive stakeholders are approaching the gear mesh source by approximate linear tools. Recent works have shown that this methodology has limitations and leads to inaccurate results. This may be a major concern. A few examples will illustrate this risk and show that further simulation developments are necessary.

Impact of metro vibrations on people: critical aspects of designing vibration mitigation interventions

A methodology for assessing and mitigating the impact of metro infrastructure generated vibration and ground-borne noise on people is described. This methodology combines techniques for analyzing vibration measurements and predictive modeling to identify effective mitigation interventions. These interventions require working on existing railway track systems and involve interruption of service, unlike noise mitigation interventions that can be implemented without interfering with rail and road infrastructure. For this reason, it is important to identify the most effective mitigation techniques to minimize the impact on the population and simplify on-site implementation. The methodology was applied in Milan metro lines where the vibration level was estimated, and a vibration mitigation system was designed. The vibration phenomenon was quantified through accelerometric measurements taken in several buildings affected by the disturbance from vibration. The measured vibration levels were compared with reference level established by standards. The maximum difference obtained from this comparison was used as input data for the design of the mitigation intervention. The vibration mitigation interventions involve increasing the total mass and elasticity of the existing system. Their effectiveness was verified through numerical calculation using parametric software confirming the required amount of mitigation.

Lightweight waveguide absorbers based on spiral acoustic black holes for reducing structural vibrations in mechanical systems

We present an ABH-based solution to address challenging industrial problems related to structural vibration and vibration-induced noise. To tackle those problems, we utilize lightweight waveguide absorbers (WGAs) based on spiral acoustic black holes (ABHs). The WGA is designed by combining a spiral acoustic black hole with a rod to absorb flexural waves and dampen the vibrations in dynamic systems. The WGAs are customized to industrial needs, pursuing both high-damping performance and lightness. Specifically, we design non-identical configurations of WGAs by taking multiple or broadband target frequency ranges into account. We then determine optimal attachment positions and directions of the designed WGAs while considering constraints on installation space and total weight of WGAs. Numerical and experimental results verify the feasibility to meet the requirements of industries through the use of WGAs, thereby opening up the possibility of practical applications to real-world problems.

Development of operational tire-suspension contact force analysis using frequency based substructuring

With increase of EVs, we need to improve road noise performance as background noise caused by engines are reduced. On the other hand, to predict road noise performance, it is necessary to consider both tire and vehicle vibration characteristics, and various prediction techniques have been reported. Frequency based substructuring method (FBS) can predict the road noise performance by combining vibration characteristics of components of a vehicle, and is effective for reducing the development cost because it can clarify the development goals of both OEM and suppliers. With this regard, FBS is very useful for implementing MBD in the development of vibration noise. In this paper, for the road noise up to 500 Hz, in which structure-borne noise is the main source, we calculate the coupled vibration characteristics consisting of two subsystems: a tire (including a rigid wheel) and a suspension, by calculating in the rolling state for each subsystem by simulation and combined them by FBS. To evaluate the method, we compared the results with the vibration characteristics of the entire system in the rolling state. In particular, we calculated the transfer function of a tire in a rolling state to take the effect of tire rolling into account .

A study on the difference in noise reduction between rear and side microphone on CPX measurement method through sound absorption frequency analysis

The road noise evaluation method in Korea is based on the 'noise vibration process test standard' by the Ministry of Environment. In this evaluation method, the noise felt at the sound-receiving point is measured as LAeq. Recently, in order to clarify the noise measurement standards for low-noise pavements, an international standard (ISO11819-2, CPX method) was first introduced in the Porous Pavement Guidelines of the Ministry of Land, Infrastructure and Transport. According to ISO, CPX measurement method adopts side microphones as mandatory, and the rear microphone as optional. Due to the difference in location noise level is different, causing confusion in the road noise evaluation method. Researchers have published several studies in the past that the rear microphone is highly correlated with the equivalent noise level method based on the Korean standard. As a follow-up study to the above results, this study examines the characteristics and causes of the frequency spectrum of the rear and side microphones in the case of dense asphalt pavement and porous asphalt pavement and derives the results through frequency analysis of the sound absorption coefficient test to determine and to contribute improving reliability and institutional rationalization of the CPX measurement method.

Improving the mechanical and tribological properties of Cu matrix composites by doping a Mo2BC ceramic

Cu matrix composites (CMCs) are widely employed for tribological applications such as in sliding bearings and electrical contact fields. However, the Cu matrix needs to be modified to improve its mechanical and tribological properties. In this study, CMCs reinforced with Mo2BC ceramic particles (10–30wt.%) are prepared via the spark plasma sintering (SPS) route method. In comparison with the plain Cu sample, when the content of the Mo2BC particles increased to 30wt.%, the Vickers hardness, yield strength, and tensile strength of CMCs increased by 196%, 157%, and 588%, respectively. Fine grain and load transfer strengthening mechanism are considered the main strengthening mechanism. Introducing the Mo2BC ceramic effectively reduces friction and wear as well as the frictional noise vibration of CMCs. Incorporating Mo2BC ceramic into the Cu matrix can elevate the load-bearing ability, inhibiting mechanical and adhesive wear. In addition, the composite exhibits superior friction and wear properties as the content of Mo2BC ceramic increases gradually up to 30wt. %, where the friction coefficient and wear rate are as low as 0.35 and 3.25 × 10−6 mm3/Nm, respectively. A layer of tribo-film containing Fe2O3 derived from the counterparts and induced by the tribo-oxidation reaction can provide a lubricating effect. Considering the superior mechanical and tribological properties, the as-prepared CMCs could be an attractive alternative material for sliding bearing fields.

Acoustic Noise Mitigation in Slip Angle Controlled DTC of Open-End Winding Induction Motor Drive Using Dual Randomized AISPWM for EV Application

Low vibration and acoustical noise as well as effective DC link usage are the demands of industries and Electric Vehicles (EV). Direct Torque Control (DTC) of Induction Motors (IMs) meet the EV and other modern industry requirements. Still, flux as well as torque swings lead to higher acoustical noise. Consequently, EVs as well as working place noise have become major concerns, affecting the health of individuals. Efficiency of dc link use is improved by Space Vector Pulse Width Modulation (SVPWM). Yet, SVPWM is not efficient in lowering acoustical noise. Different RPWM techniques can lower acoustic noise. Still, the lower degree of randomisation makes the noise reduction difficult. This work presents a Hybrid Dual Random PWMs (HDRPWMs) based Alternate Inverter Switching (AIS) strategy for Slip-Angle Controlled Direct Torque Control of an Open End Winding IM Drive (OEWIMD). This technique is aimed to lower the acoustical noise for EVs. The intended PWMs seek to show how well HDRRPWMs distribute the acoustical noise spectra in contrast to conventional techniques.