Ground-borne Noise Research Articles

Experimental assessment of isolation performance of a building above metro lines: a case study with dual isolation levels

This paper presents an assessment of the acoustic performance of a five-story residential building constructed directly above a metro line in Prague. The building has been isolated at two levels: first, on top of the distribution beams above the metro tunnel and secondly, at the ground floor. The assessment of the building's performance has been conducted by a direct measurement of ground borne noise radiated inside the rooms and evaluating the vibration transmission loss through the isolation system. The transmission loss assessment was carried out using two different test setups. Firstly, during train pass-byes, ground borne vibrations were simultaneously measured at various locations above and below the vibration cut. Secondly, at the same measurement points, the vibration levels were measured using hammer impacts. Finally, the transmissibility obtained from both test setups was compared and discussed. Additionally, ground borne noise levels were measured inside rooms on different floors above the vibration cut. To identify noise events exclusively associated with train pass-byes, data obtained from synchronized vibration measurements at the center of a room inside an apartment were used. Finally, the measured noise levels were compared with the limit values of noise exposure recommended by the Czech standards.

Towards situation dependent radiation efficiency

Designing buildings to protect inhabitants against ground-borne noise from railway lines or other outdoor ground vibration sources has become a subject of importance. Prediction methods to tackle such a problem are under discussion within a European task group (CEN/TC126/WG2/TG1). From velocity response of floors and walls, the structure-borne sound level has to be evaluated; the linking quantity is the radiation efficiency. In the frequency range of interest, i.e. covering the one-third octave bands from 16 to 250 Hz, rooms modes exist for standard size living spaces in building. A parametric investigation is carried out to evaluate the effect of the room modes on the radiation efficiency. In a first step, a modal approach is used to estimate the radiation efficiency for different room sizes, heavy floor and light wall types. Randomly positioned forces are considered as excitation on these structural elements. From these results, the situation dependent radiation efficiencies are investigated and discussed.

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.

A framework in three different project stages to predict ground-borne noise of trains in railway tunnels

Trains passing through tunnels cause noise and vibrations that negatively affect nearby residents. Developing a model to effectively predict ground-borne noise in nearby buildings faces challenges in the early project phases due to limited available data. This study suggests a framework for three stages based on precision and available information: location stage, planning stage, and construction stage. The first two stages correspond to determining the location and designing the railway track. The third stage involves the construction of the railway tunnel where more detailed information may be acquired by measurements on site. The prediction model presented here is formulated as a source term and correction terms considering train type, track type, track treatment, train speed, distance attenuation, foundation coupling, and floor-to-floor attenuation. Moreover, instead of using safety factors, which may cause unnecessary increase in project costs, the concept of combined uncertainty is applied here, using the estimated standard deviation of each term and the root sum of squares. Consequently, a comprehensive ground-borne noise prediction model adapted to various stages and handling uncertainties is proposed.

Feedback from acoustic and vibration mitigation measures on buildings along railways

Designing buildings very close to existing railway track with heavy commuting traffic requires special attention regarding noise and vibration. The situation reported in this paper is that of an existing embanked railway line 20 km East of Paris, where buildings have been constructed right above the embankment and not too far from a station. Consequently, as the tracks cannot be modified, the mitigation measures have been taken on the receiver side, i.e. the buildings. The noise and vibration mitigation measures implemented in buildings in order to limit occupant annoyance are first described. Then, acoustic and vibration measurements inside and outside of the considered buildings are discussed and results examined with respect to the implemented mitigation solutions. Finally, measured vibration and sound levels are compared to target values under discussion for new regulation on ground borne-noise and vibration levels in buildings along railways.

Ground-borne noise and vibration: classification of railway vehicles based on a track-independent vehicle indicator

Ground-borne noise and vibration: classification of railway vehicles based on a track-independent vehicle indicator

A track-independent vehicle indicator for ground-borne noise and vibration emission classification

Ground vibration from railways is increasingly recognised as a source of annoyance to lineside residents. However, in contrast to airborne noise, there are no standard test procedures to quantify the vibration emission of trains. This is compounded by the fact that measurements of vibration are highly sensitive to the properties of the test site. Here, to help overcome this, a ‘track-independent vehicle indicator’ (TVI) is proposed that can be used to classify railway vehicles in terms of their ground-borne noise and vibration emission. Two different formulations of TVI are proposed, one related to feelable ground-borne vibration and the other to ground-borne noise. The proposed TVIs are based on the force density at the railhead, which may be obtained indirectly from measured ground vibration due to train passages together with a measured line source transfer mobility at the test site. Corresponding frequency weightings are defined to mimic the sensitivity of human response to ground vibration or ground-borne noise. Each TVI is a single number quantity, defined as a sum over all relevant frequency bands of the frequency-weighted force densities. The proposed performance classification of different vehicles can be achieved by comparing the relative differences of their TVIs. The force density is chosen as the basis of the TVIs because, in contrast to the vibration levels, it is relatively independent of the test site. Nevertheless, some restrictions should be applied to the site to avoid undue influence from the track or ground properties. A transposition procedure can also be used to convert results to a standard situation to reduce this influence. A series of test cases is used to demonstrate the potential of the TVIs to classify railway vehicles in terms of their ground-borne vibration and noise emission.

Analysis of uncertainty and variation in underground train-induced vibration based on measured data

Ground-borne noise and vibration from metro trains can cause human distress/annoyance, affect the growth of animals and plants, and also negatively affect real estate property values. Before construction, the common prediction methods for the environmental vibration caused by metro trains are physical model prediction and analogy test. However, the rationality of the analogy test and the factors that need to be considered in the simulation prediction have not been systematically tested and studied. In order to solve this problem and provide experimental reference for the prediction model, one of China’s subway were systematically tested to investigate wheel roughness, rail roughness, train running speed, axle load changes, the vertical and lateral contributions, and the influence of random factors existing in the test on the vibration of subway operating environment, the following conclusions are obtained: (1) The test state randomness (random factors in the test, such as wheel-rail contact points, roughness phase, etc.) mainly affect frequencies below 31.5 Hz segment, mainly from the randomness of the wheel roughness phase or the variation of the spatial position of different contact points during actual operation, which result in large different of long-wave roughness of the wheel and rail; (2) The wheel-rail lateral force also has great influence on the environmental vibration. When establishing the environmental vibration prediction model, it is necessary to consider the state that the train reaches the straight line after passing through the curve, and the influence of track lateral irregularity; (3) The impact of wheel roughness on the environmental vibration is very large. Basically, it has an impact on the whole evaluation frequency band of environmental vibration.

Investigating the impact of tunnel geometry on ground-borne noise and vibration from underground railways

Existing methodologies offer a robust basis for predicting ground-borne noise and vibration effects arising from typical railway tunnel structures constructed using tunnel boring machines. However, the literature offers less clarity on how variations in tunnel geometry—such as those found in mined sections or crossover caverns—may influence these vibration levels. This paper addresses this knowledge gap, employing finite element modeling to conduct a comprehensive parametric study of variations in tunnel geometry. The research objective is to discern the influence these deviations from standard tunnel cross sections have on predictions of ground-borne noise and vibration. The results from this investigation offer valuable insights, challenging the notion that existing methodologies can be universally applied across all tunnel configurations. Our findings underscore the critical role that nuanced tunnel geometries play in shaping ground-borne noise and vibration profiles, emphasizing the need for more granular predictive models that consider these variations. This study is poised to significantly contribute to the understanding and prediction of ground-borne noise and vibration in railway systems, facilitating improved tunnel design, minimizing potential disturbances, and enhancing overall system performance.

Design and development of SiteHive MEMS based system for real-time vibration monitoring

Construction projects need to proactively manage their works that may cause vibration impacts to nearby structures and stakeholders. Risks of vibration include cosmetic and structural damage to buildings and threats to human comfort. The advent of MEMS accelerometers offers significant opportunities to improve on traditional vibration monitoring practices based on geophones. Geophones measure velocity which preclude acceleration based measurements and calculations like vibration dose value (the measure for human comfort), groundborne noise, and auto-levelling. The inability to capture these results means additional monitoring devices are required to capture all key measurements. MEMS-based vibration monitoring systems can be much cheaper, smaller, and more power efficient than traditional vibration monitoring systems. This enables easier installation, greater mobility, and more monitoring to be conducted. SiteHive has worked extensively with the National Measurement Institute (NMI) and the University of Technology Sydney (UTS) to test and validate the efficacy of the MEMS-based accelerometers and develop a calibration system for MEMS-based devices. This paper will outline the design research and findings that have gone into this development, results from field testing, and details on the value offered by this innovation.

Railway Ground Borne Noise (GBN) Reduction by Rail Dampers

Railway GBN impact has raised increasing concerns due to underground transportation expansion. Reducing train speed or replacing standard baseplates with high resilient ones are adopted for GBN control. Both mitigations are not satisfactory considering the installation difficulty and limited performance, e.g., only ~3dB noise reduction for 30% train speed reduction. On the other hand, FST (Floating Slab Track) are commonly used. In many cases, to accommodate the FST, tunnel diameter is enlarged for the TBM (Tunnel Boring Machine) tunnel section. Also, rail dampers are used for air-borne noise control, but never used for GBN control due to its relatively small mass. P2 resonance is a main cause of railway GBN. It is a simple harmonic motion of a lump mass (wheel and rail combined) oscillating on top of resilient baseplates. Laboratory test was conducted with a 6m fastened rail and a ~450kg mass to simulate train wheel and track system. A retrofit rail damper with TMD (Tuned Mass Damping) oscillators was tested. The mass of TMD oscillators along the rail with ~2m effective length of P2 resonance is more than 10% of the wheel. Around 7dB vibration reduction was recorded at the rail and floor when allowing the TMD oscillation.

Track Decay Rate (TDR) Measurement Method for Reactive Damping by Tuned Mass Damper (TMD)

TDR measures the rate of vibration decay along rail in dB/m. Higher TDR leads to lower noise radiation. However, new railways are often having low TDR due to the use of resilient fasteners (to provide vibration isolation between rail and supporting structure for ground borne noise concerns), which leads to high noise radiation. Rail damper is used to increase TDR (thus reduces railway noise), where TMD is an efficient damping mechanism dissipating the vibration energy of the rail. TMD provides reactive damping force, maximised after a few cycles of oscillations. TMD force is stronger with continuous excitation than impulse excitation. For convenient purposes in the industry, TDR measurements are primarily conducted by impulse method, which do not allow sufficient time to include reactive TMD force. Therefore, impulse excitation TDR is smaller than continuous excitation TDR. Continuous excitation TDR is considered to reflect more of the real case of wheel/rail interaction excitation during train running. Besides, TDR in terms of time decay in dB/s is an alternative approach for evaluating noise performance of the rail. This paper presents TDR measurement results under different conditions, e.g., impulse excitation against continuous excitation; freely supported short rail (~6m), short rail (~6m) with resilient fastener support as well as site measurements in continuous welded rails.

Ground-borne noise and vibrations in buildings induced by pile driving: An integrated approach

The use of pile driving techniques in urban environments demands accurate methods to predict and mitigate the potential discomfort of residents of neighboring buildings. In this context, a numerical model to predict ground-borne noise and vibrations in buildings induced by pile driving is proposed in the present paper. The model is based on a sub-structuring approach, in which the entire propagation medium is considered, from the vibration source to the receiver.The pile-ground domain is simulated by an equivalent linear FEM-PML approach formulated under axisymmetric conditions taking into account the pile-hammer interaction. The building simulation is performed using a 3D FEM approach, adequately adapted to include the soil-structure interaction, while the acoustic field induced by the structural vibration is analysed using a 3D MFS model. The levels of ground-borne noise and vibration inside the building resulting from pile driving are assessed through an application example, clearly showing the potential of the proposed methodology.

Reducing ground borne noise due to railways: A practical application

The construction of new buildings very close to existing tracks, with heavy commuting traffic, requires careful design. Such projects must be accompanied with noise and vibration reduction measures. The practical case here considered has been analysed by first assessing the existing situation prior to construction (type of soil and traffic). In a second stage, we have proposed and quantified solutions to reduce vibration and ground-borne noise levels inside the buildings. A 2.5D FEM/BEM commercial software (Mefissto), developed by CSTB, has been employed in what is a very challenging numerical context: multi-layered ground, large multi-levels buildings, large frequency range (10–250 Hz). In every situation, the use of an original 2.75D approach leads to the low frequency noise levels inside the buildings. As the trackwork cannot, in this case, be modified the solutions tested consist in inserting different types of barriers in the ground or in inserting either spring of resilient bearings (decoupling) in the lower part of the structure. Results are compared to target values in terms of vibration and ground-borne noise levels selected in order to limit dwellings occupants’ annoyance. Satisfactory results can only be achieved with the use of the decoupling solution.

Annoyance Based Vibro-Acoustic Comfort Evaluation of as Summation of Stimuli Annoyance in the Context of Human Exposure to Noise and Vibration in Buildings

This paper presents the issues of assessing the comfort of people staying indoors who are exposed to vibrations and material noise caused by vibrations of partitions like floors and walls (ground-borne noise). Current criteria in the evaluation of vibrational and acoustic comfort cannot be assessed in the context of the simultaneous occurrence of stimuli such as noise and vibration. Railway transport, including passenger and cargo transport, is becoming increasingly prevalent, and new railway lines are being planned for environmental reasons. Sometimes, there are changes in stimuli produced by existing railway lines. For example, high-speed trains appear on an old railway track. Such a situation appeared on the Central Railway Line in Poland, which is still used by old trains, yet its operator plans to raise their speed limits. The analysis of the problem of the simultaneous occurrence of stimuli presented in this paper was based on measurements performed in a residential building located near the Central Railway Main Line in the city Zawiercie. Noise and vibration as the analyzed stimuli in both cases meet comfort requirements, yet when exposure to two stimuli was considered, comfort may be at risk.

A transferable method for estimating the economic impacts of track interventions: Application to ground-borne noise reduction measures for whole sections of route

The environmental impacts of noise and vibration are becoming increasingly important in the assessment of new and upgraded railway routes. Vibration from railways propagates through the ground to nearby buildings where it may cause annoyance as feelable vibration or as re-radiated noise. To tackle the adverse effects of ground-borne noise a range of possible interventions are available, including softer rail pads, under-sleeper pads and under-ballast mats. The installation costs of such interventions are generally higher for the higher-performing track types. Additionally, there are potential effects on track maintenance costs which may be positive or negative, for example by reducing sleeper damage or increasing the need for ballast tamping. This study presents a socio-economic analysis of the effects of several interventions to reduce ground-borne noise. By selecting a whole route, the installation and whole-life costs are assessed using Network Rail’s Vehicle-Track Interaction Strategic Model (VTISM) and these are offset against benefits in terms of reduced social costs. Ground-borne noise is predicted at various distances from the alignment using the Modelling of Train Induced Vibration (MOTIV) model and the effect of track interventions is determined as insertion loss spectra. The re-radiated noise within a typical domestic building is then estimated using generic building transfer functions. Geographic Information System tools are used to estimate the population affected by ground-borne noise and their expected level of exposure. The methodology is illustrated using a case study route between Brighton and Portsmouth in the South of England.

The shadow effect on the ground surface due to vibration transmission from a railway tunnel

Abstract The prediction of the ground vibration transmitted from tunnels to neighbouring buildings is a vital step in the assessment of the ground-borne noise in buildings. In empirical models it is commonly assumed that the level of ground vibration reduces monotonically with the distance away from the tunnel alignment. In reality, a ‘shadow’ zone is observed above the tunnel. This is first illustrated using measurements made above an operational railway line. To understand and characterise this effect, a study has then been carried out using various simulation models. Using an analytical model for the response to a point force acting in a homogeneous full-space, it is shown that the response is principally in the form of shear waves which radiate to the side rather than compressional waves which radiate in the direction of the load. This leads to a ‘shadow’ zone forming above a certain frequency, even in the absence of a tunnel and the absence of a free ground surface. The ground surface is next introduced by considering the response of a half-space to a point force, using a semi-analytical model. This is shown to exhibit similar behaviour although with differences caused by the free ground surface. Finally, a numerical 2.5-dimensional finite element/boundary element model is used to determine the response of a half-space ground to a force acting at the bottom of a concrete tunnel. The extent of the shadow is defined as the width to the point of maximum response. This depends largely on the depth of the excitation force and the shear wave speed of the soil. Although similar features are found with or without the tunnel, the presence of the tunnel structure causes a reduction in the shadow width, and the level difference within the shadow region is slightly increased. A tunnel with a smaller diameter leads to an increase in the frequency at which a given shadow effect occurs, but the tunnel lining thickness has negligible influence. The existence of shadow effect should be taken into account when making predictions of ground vibration using empirical models.

Causes and methods of applying building protection from the impact of rail-transport

The paper presents an attempt to unify the issue of acoustic vibro-insulation used in the design of buildings and its impact on the building structure based on a calculation example. While the methodology of selection and methods of acoustic insulation of buildings from airborne traffic noise, as well as methods of limiting the structure vibrations to acceptable levels are widely recognised and applied, there is no generally accepted methodology of limiting the secondary noise that can be generated in buildings as a result of vibrations transmitted through the ground to the foundations and structure of the building (so-called ground-borne noise or re-radiated noise).

Simulation on metro railway induced vibration. Part I: effect of out-of-round wheels

This paper discussed the effect of out-of-round wheels on simulation of rail dynamic behavior in the frequency range for ground vibration and ground-borne noise. A train-track interaction model was built by software Simpack and Abaqus. The input roughness was measured from a worn wheel and was applied moving on perfect smooth rail surface in different train speeds. Simulation results indicated that out-of-round wheel would affect the calculation result that could not be neglected, as the affected frequency range would be lower enough to influence the ground vibration (1-80 Hz) and ground-borne noise (16-250 Hz).

Modelling, simulation and evaluation of ground vibration caused by rail vehicles

ABSTRACTThere is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequence. Compared with airborne noise, the related problem of ground vibration is much more complex. The properties of the ground vary significantly from one location to another. There is no common assessment criterion or measurement quantity and no equivalent to the noise maps. Ground-borne vibration is transmitted into buildings and perceived either as feelable whole-body vibration or as low frequency noise; it can also affect sensitive equipment but it is generally at a level that is too low to cause structural or cosmetic damage to buildings. A review is given of evaluation criteria for both feelable vibration and ground-borne noise, empirical and numerical prediction methods, the main vehicle and track parameters that can affect the vibration levels and a range of possible mitigation methods.