Vibration Velocity Level Research Articles

Integration of a hybrid vibration prediction model for railways into noise mapping software: methodology, assumptions and demonstration

AbstractWithin the SILVARSTAR project, a user-friendly frequency-based hybrid prediction tool has been developed to assess the environmental impact of railway-induced vibration. This tool is integrated in existing noise mapping software. Following modern vibration standards and guidelines, the vibration velocity level in a building in each frequency band is expressed as the sum of a force density (source term), line source transfer mobility (propagation term) and building correction factor (receiver term). A hybrid approach is used that allows for a combination of experimental data and numerical predictions, providing increased flexibility and applicability. The train and track properties can be selected from a database or entered as numerical values. The user can select soil impedance and transfer functions from a database, pre-computed for a wide range of parameters with state-of-the-art models. An experimental database of force densities, transfer functions, free field vibration and input parameters is also provided. The building response is estimated by means of building correction factors. Assumptions within the modelling approach are made to reduce computation time but these can influence prediction accuracy; this is quantified for the case of a nominal intercity train running at different speeds on a ballasted track supported by homogeneous soil of varying stiffness. The paper focuses on the influence of these parameters on the compliance of the track–soil system and the free field response. We also demonstrate the use and discuss the validation of the vibration prediction tool for the case of a high-speed train running on a ballasted track in Lincent (Belgium).

Relationships and statistics between various vibration metrics, derived from a large set of measured train pass-bys

The impacts of groundborne vibration (GBV) and sound (GBS) induced by railway infrastructure are assessed across the world through different metrics. Many national and international standards can be found for assessing GBV, based either on acceleration (UK, Spain, etc.) or velocity metrics (Germany, USA, etc.). Various frequency and/or time-weightings can be used, and different quantities (running RMS or highest levels) are also considered. Direct comparison between the various assessment criteria and measured metrics is, therefore, difficult. Although no international standard defines GBS criteria, many guidelines suggest such a criterion through a relationship between GBS levels and vibration velocity levels on room surfaces. Different quantities are often used, even for neighboring projects: London’s Crossrail (now Elizabeth Line) and Northern Line extension impact assessments both used maximum vibration velocity levels but with different time weighting (slow and fast, respectively). Arup has amassed a large dataset of vibration measurements through its involvement in many railway schemes over the years. For each of the thousands of train pass-bys, measured at different distances, infrastructure types, operation, and ground conditions, the most common European and North American GBS and GBV metrics are derived and compared to each other to develop statistical relationships and associated uncertainties.

Application of vibration insulating mats in tram track construction

The article deals with a feasibility study methodology for applying vibration insulating mats in tram track construction. The method for calculating railway track vibrations from the rolling stock with axial loads of 220-250 kN/axle at speeds of 50-90 km/h is presented. The dependences of the vibration amplitude obtained are approximated for tram loads, and the performed measurement errors are calculated. Based on the calculations, the dependence of vibration amplitudes on the distance to the tram track for frequencies of 31.5 and 63 Hz is obtained. In conclusion, a recommendation on the use of vibration isolating mats for ensuring acceptable values of the vibration velocity level is given.

Influence of shaft combined misalignment on vibration and noise characteristics in a marine centrifugal pump

Shaft combined misalignment is the main form of shaft misalignment fault in a marine centrifugal pump. To investigate the influence of shaft misalignment on the vibration and noise of marine centrifugal pumps, a marine pump is experimentally measured under normal condition and shaft combined misalignment condition. In this paper, the frequency domain characteristics of vibration and noise are analyzed by Fast Fourier transform technique. The characteristics of axis orbit, the spectral characteristics of vibration and noise, and the One-Third octave spectral distribution characteristics are also comprehensively compared. Results show that after shaft combined misalignment occurs, the maximum amplitudes of 1APF (axial passing frequency) in the X and Y directions at M1 increase by 35.06% and 24.04%, the maximum amplitudes of 2APF in the X and Y directions at M1 increase by 2.61 times and 2.61 times, and the axis orbit shows a clockwise variation of the “8” shape. As the flow rate decreases, the shape of an “8” of the rotor axis orbit becomes progressively flatter. The maximum Overall vibration velocity level (OAVL) of M2 and M5 decreases by 12.03% and 1.79%, and the maximum OAVL of M3 and M4 increases by 6.52% and 2.27%. The frequency domain amplitude of M6 increases significantly in 1APF and 2APF, and the maximum increases are 12.41% and 2.24% at different flow rates. The overall sound pressure level of M6 increases by 0.42% at 0.6 Qd. These findings indicate the vibration energy of M1-M5 and noise energy of M6 are related to the running condition. The axis orbit of M1 shows the shape of 8, which can significantly judge the misalignment of the shafting. Then, combined with the amplitude variation of 1APF and 2APF of the M2-M6 spectrum, the comprehensive misalignment of shafting can be further judged. The above discoveries provide reference to the diagnosis of shaft combined misalignment fault that occurred for the marine pump.

Investigation of Fault Effect on Blast-Induced Vibration

The propagation of blast-induced vibration velocity in the rock mass varies depending on many parameters. Due to a large number of effective parameters and the variability in the rock mass environment, it is not possible to create a vibration velocity propagation model using all of these parameters. On the other hand, it is important to determine the blast vibration velocity level in urban infrastructure works and mining operations near settlements. Recent studies on the subject have been interested in the determination of blast-induced vibration velocity by the back analysis estimations of advanced statistical approaches and artificial intelligence approaches. However, sudden changes in rock mass properties such as fault zones cause significant errors in the advanced statistical approaches functions used at the level of blast-induced vibration velocity. In this study, the variation of the blast-induced vibration velocities under the influence of the fault zone has been discussed. There is a fault zone along the northwest line of the Quarry boundary. The influence of the fault zone on the blast-induced vibration propagation was determined by comparing the vibration velocities behind the fault zone with the vibration velocities in the non-fault zone. Accordingly, it has been concluded that the fault zone has the potential to create significant differences due to the reflection/refraction of surface waves (Rayleigh and Love waves) in vibration velocity values in areas close to the fault zone have the potential.

Train-induced floor vibration and structure-borne noise predictions in a low-rise over-track building

Frequent train operations in metro depots can have adverse effects on the buildings’ occupants in terms of feelable vibration and noise. A method is proposed to predict vibration transmissions from columns into girders and subsequently into the floors. This method is quite efficient in modeling and computation, saving engineers time and computational cost. It is highly useful in the design phase for identifying undesirable feelable vibration and audible noise within buildings and for developing mitigation measures that improve human comfort, operation of sensitive equipment, and manufacturing.Train-induced ground-borne vibration in metro depots transmits into the upper floors of over-track buildings primarily through axial waves in the supporting columns. The vertical vibration of a column at a floor inputs mechanical power into the attached girders based on their impedance at the column. An analytical model of the girder impedance is developed that accounts for the coupling to the floor and for composite action where in-plane deformation in the floor stiffens the girder. Along with the measured vibration velocity levels at the columns, impedances of the coupled floor and girders are used to predict the mechanical power input at individual columns into the girders. The input mechanical power generates bending waves in the girders with subsequent transmission out into the attached floor along their length. The resulting average floor vibration levels in the bay are predicted in response to the total mechanical power input, which in turn radiate noise from the floor structure into the room.The overall model from vibration inputs at the columns to room noise levels was applied to a 4-story over-track building during train passbys under the building in the Qianhai Metro Depot in Shenzhen, China. The predicted average floor vibration levels and room noise levels were in good agreement with their corresponding measurements.

Computational analysis of the influence of the perforated plate on sandwich transducer in sound radiation performance

To improve the acoustic radiation performance of the sandwich transducer, a perforated plate is added to the radiation end of the transducer. The improved effect of the addition of a perforated plate on acoustic radiation performance of the transducer is studied. First, based on electromechanical equivalence principle, when a perforated plate is attached to a piston vibrator, the expressions of the vibration velocity of radiation surfaces, directivity index (DI) and radiated sound power are derived. Thus, the influences of the perforated plate on the sound radiation performance of the piston vibrator are analyzed. Then, the perforated plate is attached to the radiation surface of a sandwich transducer, and the electromechanical equivalent circuit of the transducer is established. Thus, the input impedance at the radiation end, vibration velocity and sound pressure level (SPL) of the transducer are derived. Further, the SPL of the transducer is calculated and the influences of the perforated plate on the transducer acoustic radiation performance with or without a matching layer are studied. And, the influences of the perforated plate on acoustic radiation performance of different operating frequency transducers are analyzed. Finally, the influences of the perforated plate structural parameters on the SPL of transducer are studied. The results show that the perforated plate with appropriate parameters could further improve the impedance matching between the input impedance and the radiation impedance at the radiation end of the transducer, thus the radiated SPL could be improved maximally. The research method is expected to applied in high-power transducer design.

GEOECOLOGICAL RISKS OF TECHNOGENIC NOISES AT LOW FREQUENCIES

The article considers the estimation and prevention problem of ecologically dangerous influence of technogenic noises generated by moving transport, such as heavy tracked and wheeled transport, railway transport. The influence on the man and the environment of a low-frequency controlled CV-40 seismic vibrator [1] used for seismological research separately is considered. The influence of vibrations located in the area of low and infra-low frequencies is estimated. The field records of technogenic noises are analyzed. Numerical analysis and estimation of levels of geoecological risks associated with seismic vibration in the ground and acoustic oscillations in the atmosphere are presented. Spectral and spectral-time analysis of technogenic noises records are performed. The main ecologically dangerous frequency areas, which are the most characteristic for these sources, are separated. The dynamics of changes of the vibration velocity level over distances for heavy wheeled and tracked types of transport has been determined.

An experimental study on the role and function of the diaphragm in modern acoustic stethoscopes

Vibrations of a diaphragm of an acoustic stethoscope in contact with a body of an auscultated patient are the source of the sound transmitted to the ears of a physician performing examination. Mechanical properties of a diaphragm can thus significantly affect the parameters of the transmitted bioacoustic signals. However, the exact relation remains mostly unclear, as the underlying phenomena involve complex effects of acoustic coupling between the diaphragm and the body of a patient. The present study introduces a detailed methodology for determining vibroacoustic behavior of a diaphragm of a stethoscope during a heart auscultation. A laser Doppler vibrometer is used to measure the velocity of vibrations at various points on the surface of a diaphragm during the examination. Synchronized recordings of electrocardiography signals are used for segmentation. Representative data sets are selected and analyzed for various kinds of diaphragms. The results show significant differences in vibration velocity levels and their distribution across the surfaces of the considered structures, but no significant filtering effects.

Vibration control of a marine centrifugal pump using floating raft isolation system

In order to study the influence of floating raft isolation system (FRIS) on the vibration characteristics of marine pump, a marine centrifugal pump with/without FRIS under the same operation condition, which specific speed is 66.7, was experimentally measured. The maximum efficiency of the pump is 75.8%, which is under 1.2 Qd. Results show that the characteristic frequencies in the vibration spectrums of the pump with/without FRIS are APF (axial passing frequency), the BPF (blade passing frequency) and its high-order harmonic frequency. After installing FRIS, under 0.8 Qd, 1.0 Qd and 1.2 Qd, the vibration intensity of the pump at inlet flange is slighter than that at pump base and larger than that at pump bracket. The vibration intensity at outlet flange is slighter than that at the pump bracket and larger than that at pump body, and the vibration intensity at connecting plate is the lowest. The vibration velocity level of pump base decreases with the increase of flow rate, the maximum vibration intensity at M1–M4 is reduced by 88% than that without FRIS, and the maximum vibration velocity of the APF at M1–M4 is reduced by 83.3% than that without FRIS.

STUDY OF WORKING CONDITIONS IN PATIENTS WITH OCCUPATIONAL POLYNEUROPATHY OF UPPER EXTREMITIES

Autonomous sensory polyneuropathy of upper extremities is one of the most common occupational diseases of peripheral nervous system. Findings of the study of working conditions in two major worker jobs in which occupational polyneuropathies of upper extremities are prevalent, namely: house-painters and plasterers, as well as mining job workers (underground miners, shaft miners, breakage face miners) are reported. Hygienic investigations envisaged detailed studies of working conditions in workers with diagnosed occupational peripheral nervous system disease. The intensity and hardness of working process, illumination level, spectral noise characteristics, noise, vibration, temperature, humidity, and air velocity levels, as well as adverse chemical concentrations in workplace air were assessed. House-painters as well as miners were found to work with pronounced physical overloads, working conditions being classified as 3.2-3.3 (2-3 degree harmful) according to indices of working process hardness. In spite of new technologies being introduced into the working process, manual labor part in these jobs still remains to be the great. Comparison of findings revealed certain differences in some characteristics of working process hardness. Working process hardness shown by dynamic and static physical load on upper extremities was found to be the most significant harmful occupational factor resulting in polyneuropathy in house-painters and plasterers. Development of polyneuropathy in miners was caused by a combination of adverse occupational factors: working process hardness, local vibration, cold microclimate. Our findings indicated the importance of the study of health state in painters and miners. Working conditions must be taken into account in the process of development of preventive and remedial measures for occupational polyneuropathy treatment.

The coupling loss of a building subject to railway induced vibrations: Numerical modelling and experimental measurements

Railway induced vibrations can be amplified or attenuated as they propagate through the foundations, floors and spans of nearby buildings. This change in vibration level, known as the building's coupling loss, is often accounted for in vibration predictions using generic, frequency independent adjustment factors. In this paper, a detailed investigation is conducted to identify methods for determining the coupling loss in new build scenarios and to investigate its dependence on various system parameters. Using the approach of separate source, propagation and receiver terms, the coupling loss is characterised as the difference between vibration velocity levels measured inside and outside the building. Three different configurations of the railway-soil-building are explored: the case where both track and building are present; the case of a new building; and the case of a new railway. In situ experiments of a building subject to excitation from nearby train passages and hammer impacts on the track are used to quantify the building response. The influence of the location of the sensors in the free field and in the building (both within a single floor and across multiple storeys) is investigated. The findings from the experimental study supports separate characterisation of the source and receiver terms, thus demonstrating that the railway can be represented by a series of on-track impacts when determining the building's coupling loss. Using this representation, a 3D building model is used to investigate the effect of dynamic soil characteristics, surface foundation type, and building geometry on the building's response to railway induced vibrations.

Flanking floor impact sound insulation in cross laminated timber model building for experiment

The Act for Promotion of Use of Wood in Public Buildings (Law No. 36 of 2010 of Japan) was enforced in 2010. The promotion of the use of wood can contribute to the prevention of global warming etc. A public building in a low layer is supposed to attempt making to timber construction by this act. Moreover it is expected that the building such as apartment houses comes to be made from timber construction. For effective use of the Japanese wood, CLT (Cross Laminated Timber), which had been used in Europe, was standardized by JAS (Japanese Agricultural Standard) as a building material in 2014. Among the objections and the troubles of buildings in Japan, the sound insulation performance is one of the most serious issues, especially floor impact sound insulation. We, however, have little knowledge about sound insulation of CLT building. Therefore we built a 3-story CLT model building for experiment and investigated the floor impact sound insulation and the flanking floor impact sound insulation. This paper presents the results of floor impact sound insulation and the surfaces vibration in a sound-receiving room. The results showed the influences of damping material, ceiling and floating on the floor impact sound insulation, and the floating floor showed possible improvements in the heavy-weight and the light-weight floor impact sound insulation of CLT building. The vibration velocity level of the ceiling was the largest. However, it is necessary to decrease the vibration velocity level of the sound-receiving room’s wall for improvement of the heavy-weight floor impact sound insulation by using damping material.

Applying constrained layer damping to reduce vibration and noise from a steel-concrete composite bridge: An experimental and numerical investigation

Structure-borne noise from railway bridges has become increasingly severe due to increased train speeds and axle loads. Constrained layer damping can suppress structural vibration and noise considerably across a wide frequency range by dissipating vibrational energy via damping layer shear deformation. This paper proposes a theoretical method of calculating the train-induced vibration and noise of a constrained layer damping-enhanced railway bridge based on the train–track–bridge coupled vibration, the modal strain energy method, and statistical energy analysis. First, the vibration responses of bridge decks were obtained via train–track–bridge coupled vibration calculations. Second, the constrained layer damping subsystem modal loss factors were determined via modal strain energy analysis and converted to damping loss factors in 1/3 octave band. Third, upon substituting the vibration energies of the decks and the damping loss factors of constrained layer damping subsystems into the statistical energy analysis power balance equations, the transmitted vibration energy results from various bridge subsystems were determined by solving the referenced equations. The structure-borne noise from the bridge was finally determined by analyzing the vibratory energies of all of the bridge subsystems using vibro-acoustic theory. Numerical analysis and field measurements of vibration and noise from a three-span steel–concrete composite bridge before and after constrained layer damping installation were performed. The predicted train-induced vibration and noise agreed well with the measured results. The stringer web and flange vibration velocity levels were reduced by 10.5 dB and 6.1 dB, respectively, and the sound pressure level at a measurement point 25 m (horizontal) from the track centerline and 1.5 m off the ground decreased by 4.3 dB(A).

An experimental study on the role and function of the diaphragm in modern acoustic stethoscopes

Vibrations of a diaphragm of an acoustic stethoscope in contact with the body of an auscultated patient are the source of the sound transmitted to the ears of a physician performing examination. Mechanical properties of a diaphragm are supposed to significantly affect the parameters of the transmitted bioacoustic signals. However, the exact relation remains mostly unclear, as the underlying phenomena involve complex effects of acoustic coupling between the diaphragm and the body of a patient. The present study introduces a detailed methodology for determining vibroacoustic behavior of a diaphragm of a stethoscope during an auscultation examination. A laser Doppler vibrometer is used to measure the velocity of various points on the surface of a diaphragm during heart auscultation. Synchronized recordings of electrocardiography signals are used for segmentation. Representative data sets are selected and analyzed for various kinds of diaphragms. The results show significant differences in vibration velocity levels and their distribution across the surfaces of the considered structures. In this regard, it is also shown that the currently available solutions can be significantly improved by using structures better matched to the acoustic impedance of a body.

The impact of changes in the geometry of a radial microturbine stage on the efficiency of the micro CHP plant based on ORC

The overall efficiency of ORC systems depends on a number of factors, but it goes without saying that the efficiency of the expansion device is one of the most important ones. The article presents the impact of modernization of the first stator stage of a micro turbogenerator on the following efficiencies: exergetic efficiency, Carnot efficiency, microturbine internal efficiency and ORC cycle efficiency. The thermal and flow characteristics for three heat exchangers (i.e. condenser, evaporator and regenerator) were shown. The paper also includes the graphs presenting the current, voltage and electric power generated by the turbogenerator during its operation in the organic Rankine cycle with regeneration. A low-boiling fluid was used as the working medium. During the research, vibration measurements were carried out on the casing of a vapour microturbine. They aimed at monitoring the machine operation so as to detect any dynamic problems (e.g. defects or malfunction). The measurement results in the form of RMS vibration velocity levels were presented and discussed.

Numerical calculation of the interior noise for the high-speed transportation under coupled multi-physical field excitations

A finite element model of a high-speed transportation was constructed, including its body in white (BIW), and traction system. And an analytical scheme on the interior structural radiation noise of a high-speed transportation was proposed under coupled multi-physical-field excitation. Rigid multi-body dynamics, boundary element method and large-eddy simulation were employed to extract secondary suspension forces, railway noise and surface pressure fluctuations, respectively, which were coupled with the structural modals to obtain the structural vibration response and noise. The experiment of vibration and noise for the high-speed transportation was conducted at speed of 350 km/h. A measuring point of vibration was randomly selected on the floor. The tendency and amplitude of its vibration velocity level and noise obtained from the experiment and simulation agreed well with each other, which validated the precision of numerical model and coupled multi-physical-field excitation.

Research on noise prediction and acoustics design of shipboard cabin

The approach used to calculate structure surface vibration velocity and sound pressure level (SPL) is provided. Then structural vibration model and panels acoustic contribution are combined to investigate sound radiation from a vibrating structure. As for the shipboard cabin where the mariners work with high level requirement of the SPL, it’s necessary to build the boundary element model of shipboard cabin by obtaining the structural mode information and finding out characteristics of vibration velocity. Considering the effect of thin-shell-structure consoles and switchboards, the acoustic field inside the shipboard cabin and the panel contribution to the cabin are analyzed. The peak frequencies in the sound pressure spectrum at the field points and their corresponding panels with larger contributions to the cabin are found. Based on the modal shape analysis, damping is adopted to inhibit the predominant modes. In front of the console and the switchboard where the engineer on watch operate, at the height of one’s head with sitting posture and standing posture, four field points are laid out respectively. Then, the most obvious peak frequency is picked out as the frequency of attention. Vibration reducing measures like laying damping coatings and modular floating floors and so on are adopted to reduce the noise radiation of the plate in the ship cabin. Through the deck vibration transmission experiment, the damping performance of the modular floating floor is ascertained. A comprehensive assessment of the noise label in the cabin is needed to ensure that the sound pressure level meet the relevant requirements of the ship general rules.

Effectiveness of the floating slab track system constructed at Konya Light Rail

Ground-borne vibrations and noise, originated at the train/tram wheel–rail interface and transmitted through the rails to the ground, may cause significant disturbance to people passing by or residing alongside the railways. This paper presents a case study on the evaluation of the effectiveness for mitigating ground-borne vibration and noise by floating slab track system (FST). The underpass located at a major road junction in front of Konya Metropolitan Municipality building serves to thousands of people every day. The Konya Light Rail makes a curb right on top of the underpass, which generates considerable amount of noise and vibration to the environment. In this study, the noise and vibration acceleration measurements were taken before and after the FST system installment in order to evaluate the effectiveness of the isolation work. The collected acceleration data were analyzed and the resulting vibration velocity levels were compared. It was found that the vibrations and the ground-borne noise due to the passage of the trams were reduced considerably. The FST system was found to be quite successful in absorbing the vibrations. A noise level reduction up to 26dBA was measured after replacing the old rail system with FST.

Vibrational and acoustical performance of concrete box-section bridges subjected to train wheel-rail excitation: Field test and numerical analysis

For the sustainable development of high-speed railway (HSR) networks, it is becoming increasingly important to tackle usability problems, one of which is the bridge noise generated by high-frequency vibrations of bridge members owing to train wheel-rail excitation. Although concrete box-section bridges predominate in HSR infrastructures, their vibrational and acoustical performance has not been well studied. Field tests on two concrete box-section bridges, one dual-track and the other single-track, are carried out simultaneously during high-speed train passbys. Time-history and spectral characteristics of vibration velocity levels (VVLs) and sound pressure levels (SPLs) are measured and analyzed. Measured data show that the highest peaks of VVLs and SPLs for dual and single-track bridges appear at 50 and 63 Hz, respectively. High-frequency vibrations are independent of longitudinal location for bridges with uniform cross-section. The average difference between the magnitudes of VVLs (with a reference velocity of 10_9 m/s) and SPLs (with a reference pressure of 2_10-5 Pa) is about 28 dB at each frequency. A train-track-bridge dynamic interaction model is applied to determine the vibration of bridge members and the statistical relation between VVL and SPL is used to estimate the near-field bridge noise. The computed results match the measurement results. The cross-sectional bending vibration modes of box-section bridges are of two types: a top-slab-dominated mode and a bottom-slab-dominated mode. Numerical analyses show that the levels of vibration and associated noise are jointly determined by the wheel-rail contact force and cross-sectional bending vibration modes, which reach their highest peaks when the modal frequencies coincide with the frequencies of the wheel-rail contact force at high values. Adjusting the cross-sectional bending vibration modes to the frequency range of the wheel-rail contact force at low values is a feasible method to mitigate bridge vibrations and noise; for example, numerical results show that the addition of a third web in the center of the bridge cross section is effective.