Vibration Noise Research Articles

Effect of concurrent exposure to noise and hand-transmitted vibration on auditory and cognitive attention under simulated work with construction tools

Objectives. This study aimed to investigate the effects of separate and concurrent exposure to occupational noise and hand-transmitted vibration (HTV) on auditory and cognitive attention. Methods. The experimental study was conducted with 40 construction workers who were exposed to noise (A-weighted equivalent sound pressure level of 90 dB) and to HTV (10 m/s2 at 31.5 Hz), and concurrent exposure to both for 30 min under simulated work with vibrating equipment used in construction. Cognitive performance aspects were then evaluated from each individual in two pre-exposure and post-exposure settings for each session. Results. The effect sizes of concurrent exposure (HTV + noise) and separate exposure to noise on auditory attention were very close (effect size = 0.648 and 0.626). The largest changes in the difference of response time in both types of attention (selective and divided attention) were related to the concurrent exposure scenario and then exposure to HTV, respectively. The highest effects for the correct response of selective and divided attention are related to concurrent exposure (HTV + noise) and then noise exposure, respectively. Conclusion. The HTV effect during concurrent exposure is hidden in auditory attention, and noise has the main effects. The divided attention was more affected than the selective attention in the different scenarios.

IGFT-MHCNN: An intelligent diagnostic model for motor compound faults based decoupling and denoising of multi-source vibration signals

In view of the insufficient representation of single source signals for multi-point compound fault and the nonlinear strong coupling of vibration signals in motor transmission system, the inverse graph Fourier transform and improved multi-head convolutional neural network (IGFT-MHCNN) diagnostic model–based decoupling and denoising of multi-source vibration signals is proposed. The MHDCNN is constructed by improved multi-head convolution network and multi-label decoupling classifier, in which they extract multi-source signal features and decouple compound fault label information, respectively. Due to strong noise in compound fault and mapping capability of graphic signal processing method for complex data, a signal reconstruction method based on IGFT is established to remove residual noise from multi-source signals and enhance the main feature components. Two experimental cases show that the constructed model can effectively reduce vibration noise and achieve multi-label decoupling and identification of motor compound faults with strong coupling.

Band gap characteristics of bionic acoustic metamaterials based on spider web

For the purpose of low-frequency vibration isolation and noise reduction, combined with the nested mode of spider web, a new concave star bionic acoustic metamaterial was proposed in this paper. Based on the finite element method (FEM) and Bloch theory, the effects of vertex connection mode, nesting level (n), and rotation angle (α) on the band gap distribution, transmission spectrum, and isofrequency line of concave star structure were discussed. The results showed that the two-dimensional (2D) concave star structure had the lowest opening frequency of the first band gap when the vertices coincide and n = 3; when α = 45°, the three-dimensional (3D) concave star structure had the widest band gap distribution and the lowest first band gap in the frequency range within 1000 Hz. The correctness of the simulation results was verified by experiments. These findings can provide a new idea for low-frequency vibration isolation and noise reduction.

Comparative Analysis of Transmission Housings to Evaluate Whining Noise Performance

A quite cabin is always a preferred choice of the customer. Powertrain acts as a source for many noise and vibration problems in a passenger car. Transmission plays a major role in modulating the power from engine to the drive train and is exposed to a high vibration and noise environments. Hence design of transmission for low vibration & noise is need of the hour. This paper attempts to perform a comparative study of 6 housings of different design of a two-wheel drive passenger car to evaluate the vibration performance and Noise radiation characteristics by using FEM (Finite Element Method) & BEM (Boundary Element Method) & finite element analysis techniques. The authors also try to put forward a layout comparison study for the housings and conclude what design is best suited for better NVH whine performance in view of vibrations & sound radiation. These indicative results from this paper can be referred by the design & analysis engineers during early product development of the transmission.
 Keywords: Transmission, Housings, Whining Noise, Bionic Design, NVH Analysis, Durability Analysis, Study of Housings, Housings NVH Analysis

A Transportable Atomic Gravimeter with Constraint-Structured Active Vibration Isolation.

Many efforts have been taken in recent years to push atomic gravimeters toward practical applications. We demonstrate an atomic gravimeter named NIM-AGRb2 that is transportable and suitable for high-precision gravity measurements. Constraint-structured active vibration isolation (CS-AVI) is used to reduce the ground vibration noise. The constraint structure in CS-AVI ensures that the isolation platform only has vertical translation, with all other degrees of freedom (DoFs) being constrained. Therefore, the stability of active vibration isolation is enhanced. With the implementation of CS-AVI, the sensitivity of NIM-AGRb2 reached as low as 20.5 μGal/Hz1/2. The short-term sensitivity could be further reduced to 10.8 μGal/Hz1/2 in a seismologic observation station. Moreover, we evaluated the system noise of the gravimeter, and the results were consistent with our observations.

Research on the model of staggered tooth phase to reduce vibration of single-stage gear transmission system: Theoretical analysis and experiments.

Aiming at the problems of high vibration and high noise in gear transmission systems, a model of gear with staggered tooth phase structure(GSTPS) for reducing vibration is proposed. Without changing the overall structure of the gear transmission system, the purpose of reducing mesh stiffness fluctuations is achieved by staggering adjacent gears at a certain angle along the axis, thereby the vibration of the gear transmission system could be reduced. The characterization method of time-varying mesh stiffness of the GSTPS is studied. Then, the impact of different staggered tooth phases(STP) on reducing vibration of the transmission system are researched, and the basis for selecting the optimal STP are obtained. The experimental platform for reducing vibration with STP is established. And some experimental studies were conducted to validate the theoretical model.

Low phase noise self-injection-locked diode laser with a high-Q fiber resonator: model and experiment.

Low phase noise and narrow linewidth lasers are achieved by implementing self-injection locking of a DFB laser on two distinct fiber Fabry-Perot resonators. More than 45 dB improvement of the laser phase or frequency noise is observed when the laser is locked. In both cases, a frequency noise floor below 1 Hz2/Hz is measured. The integrated linewidth of the best of the two lasers is computed to be in the range of 400 Hz and appears to be dominated by vibration noise close to the carrier. The results are then compared with a model based on the retro-injected power and the Q factors ratio between the DFB laser and the resonator. This straightforward model facilitates the extraction of the theoretical performance of these sources close to the carrier, a characteristic still hidden by vibration noise.

FPGA-based interference elimination for health monitoring in dynamic environments

Since flexible wearable sensing devices are mostly used to acquire the human health information by fitting, the vibration generated by the wearer’s movement, physiological state, environment, and other dynamic factors will interfere the accuracy of collected signals. In order to solve the signal interference problem in dynamic environments, a system is needed to eliminate the strong interfering signals in disturbing scenarios in order to acquire the target signal. In this paper, a FPGA-based system is designed to eliminate the signal interference, where a PFGA chipset is served as the core hardware part, an adaptive notch filter is used to process the sensing signals and the FPGA and the host computer are interacted in real time, thus various vibration noises suffered by the flexible sensing device could be eliminated when it is applied to health monitoring in dynamic environments.

SILENCER-COOLER AS A MEANS OF REDUCING THE EXTERNAL NOISE OF THE "TRITON-01" ARMORED VEHICLE

The problem of camouflage of military equipment is extremely urgent. In this work, a certain improvement of masking properties is proposed by reducing the level of external noise for the Triton-01 armored car. The Triton-01 armored car is equipped with a remote-controlled combat module, a reconnaissance and target detection system, and an information transmission system. This armored car has a number of sources of noise, among which the exhaust system is quite powerful, that is, the noise of exhaust gases. This type of noise is reduced by appropriate mufflers. As practical studies show, at the moment the noise of exhaust gases of military equipment is not sufficiently suppressed by mufflers. We offer a developed complex muffler consisting of two mufflers connected in series: a single-chamber reactive muffler and a cooling muffler. A muffler-cooler of exhaust gas noise has been developed, which contains a hermetic housing filled with refrigerant, inlet and outlet nozzles and a gas pipe for exhaust gases, made straight along the axis of the muffler and with shaped walls that provide the maximum perimeter in a given section. Passing through the gas pipeline, the exhaust gases give off heat to the cooling medium through its walls. The developed one is structurally different from the existing silencers-coolers: the contact area of the cooling liquid with the surface of the silencer is significantly increased. As a result of the cooling of exhaust gases, the speed of movement of the latter is significantly reduced, and as a result, the level of acoustic (noise) vibrations present in these gases. The work calculates the cooling system, which should cool the exhaust gases. A proposal was made to use a refrigerant that is prepared in advance for the combat departure of an armored vehicle. There are possible options for preparing the refrigerant: the armored car itself or a specialized mobile installation.

Building structure-borne noise measurements and estimation due to train operations in tunnel

The perception of structure-borne noise is particularly salient when train passes through the tunnel under the buildings, which has a negative impact on human health. In the process of constructing buildings along metro lines, it is crucial to estimate indoor structure-borne noise levels in order to enhance design and prevent any negative impact on human comfort. This study conducted measurements of structure-borne noise, reverberation time, and train-induced vibrations in Guangzhou, China to investigate the generation, propagation, and dissipation mechanisms of structure-borne noise. An approach based on Short-Time Fourier Transform and Schroeder integral was proposed for obtaining frequency-dependent reverberation time. Additionally, a deep learning-based approach incorporating indoor vibrations, frequency-dependent reverberation time, and room parameters as inputs was proposed based on Genetic Algorithm-Artificial Neural Network. The estimated structure-borne noise levels demonstrated good agreement with measured values, indicating the feasibility of the approach. The finding of this research facilitates a clear comprehension of the generation, distribution, and dissipation mechanisms of indoor structure-borne noise for engineers while also enabling convenient acquisition of indoor structure-borne noise. The estimated noise levels can be effectively utilized during building design processes along metro lines to mitigate adverse impacts on human comfort.

Study of different cutting fluids effect on the coupling characteristics of milling noise-vibration and surface roughness of TA2 pure titanium

With the increasing use of titanium alloys, it is essential to improve cutting efficiency. However, there are various problems such as high noise, strong vibration and difficulty to control the surface finish quality in actual cutting process, which can be more serious with the increase of machining parameters. In order to obtain better machining quality and higher efficiency, the influence of cutting parameters and cutting fluid on the milling process of TA2 pure titanium under two cutting conditions that use different cutting fluid is firstly studied in this paper. The correlation between the surface roughness (SR) of the workpiece and multiple metrics which milling noise (MN) and milling vibration (MV) is further studied on the basis of experimental data. In this paper, a series of parameters that have a strong correlation with SR are selected. Then, prediction models based on Least Squares Method (LSM) and Response Surface Methodology (RSM) are established. Finally, established models are compared to find ways to improve prediction accuracy. The experimental results indicate that compared with water-based cutting fluid, oil-based cutting fluid can make TA2 workpiece obtain better and more stable cutting performance most of the time; MV has a more significant correlation with SR and is therefore more suitable for establishing prediction model; The accuracy of the prediction model that takes the multi-factor coupling effect into consideration has been generally improved and the average optimization degree of the Improved Particle Swarm Optimization (IPSO) algorithm for LSM is 2.91 %, which has good optimization performance.

Fast Force Estimation of Cable Structures Using Smartphone-Captured Video and Template Matching Algorithm

Cables are important components of long-span bridge structures, whose operation is significantly affected by cable force changes. Nowadays, cable force testing is performed by physical methods; that is, sensors are installed on the cable structure to monitor its force changes. Obviously, this strategy requires an extensive amount of time to achieve cable force calculation, which makes it impossible to monitor the force of the cable structure in real time. Meanwhile, smartphones have attracted extensive attention in the field of structural health monitoring (SHM) because of their higher cost-effectiveness than accelerometers, which include price and lifespan. Besides, many people own a smartphone, which leads to the possibility of a wider range of applications. Therefore, this paper presents a framework for the rapid estimation of the cable force of long-span bridges based on smartphones-captured video and a template matching algorithm. First, the empirical mode decomposition (EMD) method with wavelet decomposition (WD) method, that is, the EMDWD model, is constructed to extract the vibration signal of the bridge cable by eliminating the effects of smartphone vibration and environmental noise on the measured dynamic displacement, thus effectively improving the accuracy of data processing. In addition, the vibration identification model of bridge cable based on a template matching algorithm is established, and the deformation curve of cable is obtained. Finally, the frequency of bridge suspender is calculated by the Fourier transform method (FFT), and the cable force is estimated based on the smartphone-captured video.

Model-free predictive current control based on improved sliding mode disturbance observer

The motor parameters of permanent magnet synchronous motor (PMSM) can be mismatched in operation due to temperature variations and magnetic saturation. The parameter mismatch leads to a significant decrease in the robustness of traditional deadbeat predictive current control (DPCC), which leads to issues such as current static error and motor vibration noise. In this paper, a model-free predictive current control (MFPCC) method based on an improved sliding mode disturbance observer (SMDO) was proposed. The method estimated the total disturbance of the system using the improved SMDO, which could effectively suppress sliding mode chattering and accelerate the convergence speed of current errors. Subsequently, the predicted control voltage was calculated using a hyper-local model and compensated for the time delay. The experimental results demonstrated that the improved MFPCC-SMDO method generated lower motor noise compared to the traditional DPCC method when the controller’s inductance parameters are mismatched.

Mechanical and vibration characteristics investigation of the elastic ring squeeze film damper-rotor considering oil film sealing and leakage

Elastic ring squeeze film damper (ERSFD) is extensively used in industrial rotating systems due to its excellent noise control and vibration suppression characteristics. However, the oil film sealing and leakage has a profound effect on the mechanical and vibration characteristics of the ERSFD and the ERSFD-rotor during operation. The sealing and leakage reduce the axial flow of the oil film, leading to changes in the initial boundary conditions of the flow field, which in turn affects the oil film pressure and damping coefficient of ERSFD. Meanwhile, the sealing causes an increase in the oil film force of ERSFD, which in turn affects the response of the rotor system. But there is relatively little research on the impact of sealing and leakage on the dynamic performances of ERSFD-rotor. In this paper, a mathematical model of ERSFD under different sealing conditions (no end seal, complete end seal, piston ring seal, O-ring seal) is established by changing the initial boundary equations of the flow field of ERSFD and the coupled solution of the Reynolds equation of ERSFD with different sealing and leakage boundary equations is realized. Then, the characteristics of oil film pressure and force of ERSFD under different sealing conditions is studied. After that, an ERSFD-rotor model considering oil film sealing and leakage is established based on displacement compatibility conditions and force balance principles. Meanwhile, the impact of sealing and leakage on the amplitude-frequency relation and sudden imbalance of an ERSFD combined support rotor is researched. The research results reveal that good sealing can significantly increase the damping of the system, thereby reducing the vibration amplitude of the ERSFD-rotor system. In addition, good sealing conditions can also shorten the transient process of sudden unbalanced excitation. Finally, the effectiveness of some simulation results was verified through experiments on the ERSFD rotor test bench.

Quantity Monitor Based on Differential Weighing Sensors for Storage Tank of Agricultural UAV

Nowadays, unmanned aerial vehicles (UAVs) play a pivotal role in agricultural production. In scenarios involving the release of particulate materials, the precision of quantity monitors for the storage tank of UAVs directly impacts its operational accuracy. Therefore, this paper introduces a novel noise-mitigation design for agricultural UAVs’ quantity monitors, utilizing differential weighing sensors. The design effectively addresses three primary noise sources: sensor-intrinsic noise, vibration noise, and weight-loading uncertainty. Additionally, two comprehensive data processing methods are proposed for noise reduction: the first combines the Butterworth low-pass filter, the Kalman filter, and the moving average filter (BKM), while the second integrates the Least Mean Squares (LMS) adaptive filter, the Kalman filter, and the moving average filter (LKM). Rigorous data processing has been conducted, and the monitor’s performance has been assessed in three UAV typical states: static, hovering, and flighting. Specifically, compared to the BKM, the LKM’s maximum relative error ranges between 1.24% and 2.74%, with an average relative error of 0.31%~0.58% when the UAV was in a hovering state. In flight mode, the LKM’s maximum relative error varies from 1.68% to 10.06%, while the average relative error ranges between 0.74% and 2.54%. Furthermore, LKM can effectively suppress noise interference near 75 Hz and 150 Hz. The results reveal that the LKM technology demonstrated superior adaptability to noise and effectively mitigates its impact in the quantity monitoring for storage tank of agricultural UAVs.

Design and performance of an ultrahigh vacuum spectroscopic-imaging scanning tunneling microscope with a hybrid vibration isolation system.

A spectroscopic imaging-scanning tunneling microscope (SI-STM) allows for the atomic scale visualization of the surface electronic and magnetic structure of novel quantum materials with a high energy resolution. To achieve the optimal performance, a low vibration facility is required. Here, we describe the design and performance of an ultrahigh vacuum STM system supported by a hybrid vibration isolation system that consists of a pneumatic passive and a piezoelectric active vibration isolation stage. We present the detailed vibrational noise analysis of the hybrid vibration isolation system, which shows that the vibration level can be suppressed below 10-8 m/sec/√Hz for most frequencies up to 100Hz. Combined with a rigid STM design, vibrational noise can be successfully removed from the tunneling current. We demonstrate the performance of our STM system by taking high resolution spectroscopic maps and topographic images on several quantum materials. Our results establish a new strategy to achieve an effective vibration isolation system for high-resolution STM and other scanning probe microscopies to investigate the nanoscale quantum phenomena.

Error analysis of IMU pipeline bending strain detection based on full-scale test

The strain identification technology based on inertial mapping unit (IMU) internal detectors is currently a widely used internal detection technology for identifying pipeline bending strain both domestically and internationally. It calculates the bending strain of the entire pipeline through the detected centerline coordinate data. However, there are issues such as abnormal vibration and noise during the actual operation of the inertial navigation internal detector, as well as trajectory deviation during the detector’s operation. This issue leads to a certain deviation between the strain detected by IMU and the actual strain of the pipeline. This article utilizes a self-designed full size pipeline bending strain loading device to conduct full size pipeline bending strain tensile tests. Compare the internal detection data obtained from the experiment with the actual bending strain data of the pipeline and conduct error analysis. The research conclusion indicates that as the bending strain increases, the error between the IMU detection strain and the actual strain of the pipeline increases. When there is vibration noise, the maximum error is 0.077% for 0.33% true strain, and the maximum error rate for larger strain segments is 27.1%. The comparison between noise reduction detection data and true strain shows that when the true strain is 0.12%, 0.21%, and 0.33%, the average error is 0.0285%, 0.0315%, and 0.0555%, respectively. The research conclusion provides technical support and guidance for obtaining true strain of pipelines based on IMU internal detection in the future.

Graduate acoustics at Brigham Young University

Graduate studies in acoustics at BYU prepare students for industry, research, and academia by complementing in-depth coursework with publishable research. Coursework provides students with a foundation in acoustical principles, practices and measurement skills, including a experimental techniques and technical writing. Labs across the curriculum cover calibration, directivity, scattering, absorption, laser Doppler vibrometry, experimental methods for dynamic structures, lumped-element mechanical systems, equivalent circuit modeling, arrays, filters, room acoustics, active noise control, and near-field acoustical holography. Recent thesis and dissertation topics include active noise control, directivity, room acoustics, energy-based acoustics, time reversal, nondestructive evaluation, vibration and acoustics of aerospace vehicles, biomedical applications, flow-based acoustics, voice production, aeroacoustics, sound propagation modeling, nonlinear propagation, high-amplitude noise analyses, machine and deep learning applied to ambient noise level prediction, crowd noise interpretation, and underwater acoustic source localization, and ocean environment classification. Graduate students are expected to present research at professional meetings and publish in peer-reviewed acoustics journals. Graduate students often serve as peer mentors to undergraduate students on related projects and may participate in field experiments to gain additional experience. @BYUAcoustics

Ensuring Safe Working Conditions under the Influence of Vibroacoustic Factors on Train Crew Workers

Introduction. The increased intensity of noise and vibration of railway traffic may become not only an urgent problem in the field of occupational safety, but also a serious environmental problem in the near future due to the constant need to increase the weight of freight trains, the speed of passenger trains and the capacity of railway lines. Recently, a lot has been done to minimize the negative effects of noise and vibration in railway transport. However, the problem of exceeding the indicators of vibration noise factors remains relevant. Reducing the harmful effects helps to improve the working conditions of train crew employees and improve the comfortable conditions of transport passengers. As a rule, the main focus of the analysis is on the external impact of vibroacoustic factors on residential areas and less attention is paid to the impact on rolling stock. However, these studies do not provide a complete picture of how noise and vibration actually affect the train in motion. The aim of the study was to obtain the result of an analysis of the impact of vibroacoustic factors on train crew workers and to propose a method of comprehensive protection based on the use of vibration damping materials.Materials and Methods. In the course of the work, regulatory documents were studied, a comprehensive analysis of relevant information on this topic was carried out, and methods for calculating vibration and vibration acceleration were used. The values of the sound pressure levels were obtained using a SPM-101 sound level meter. The object of the study was a carriage of the "reserved seat" type in the process of movement. As part of the research plan, sound pressure was measured at selected sites and a class of working conditions was determined.Results. The result of the analysis of the impact of vibroacoustic factors on train crew workers indicated the need to strengthen comprehensive measures to protect them. The obtained calculation of the vibration force became the basis of the method proposed by the authors to minimize the harmful effects of vibroacoustic factors, which was based on the use of vibration and sound insulation materials suitable for the necessary acoustic parameters in the construction of the car. In particular, it was proposed to cover the floor of the car with dense rubber and the ceiling of the car with an inorganic fiber material for sound insulation. The work also provides an economic assessment of the effectiveness of measures to minimize harmful vibration noise effects.Discussion and Conclusion. The proposed methods for minimizing noise and vibration impacts can help reduce the level of sound pressure and vibration indicators to standard values, which will significantly reduce the negative impact of vibroacoustic factors on train crew workers and railway passengers. The considered complex for minimizing vibration and noise includes a set of methods in which affordable materials based on recycled substances have found application.

Band folding induced broadband vibration suppression of star-shaped metamaterials: Theory and experiment

Metamaterials with bandgap features can block wave propagation in specific frequency ranges and thus have wide applications for vibration mitigation and noise reduction. In this study, we renovated the design of star-shaped metamaterial (SSM) to make it capable of producing lower and wider vibration bandgaps. Unlike traditional periodic truss structures in the literature, the designed SSM structure breaks the spatial symmetry, opening the degenerate points formed by the band folding effect, thereby producing extra bandgaps for vibration suppression. First of all, a finite element (FE) model of the SSM is established, and its band structures and vibration transmittance are calculated. The preliminary result validated our hypothesis, demonstrating that the proposed SSM structure created additional bandgaps for suppressing low-frequency and broadband vibrations. Subsequently, the frequency response analyses are conducted using the spectral element method (SEM) and experimental test. The effects of the structural parameters on the bandgaps of the proposed SSM are studied. In addition, we further extended and generalized the band folding design concept. We showed that one can produce more bandgaps by designing high-order SSMs. In general, this study presents an approach for designing truss structures with broadband vibration suppression performance.