Vibration Levels Research Articles

Measuring Vibrations of Subway Tunnel Structures with Cracks

In a study conducted in a metro tunnel, acceleration and displacement sensors were strategically placed along steel rails, track beds, and tunnel walls to capture real-time dynamic responses during train operations. Data were analyzed in the time and frequency domains, focusing on vibration levels and one-third octave bands. The results indicated that peak vibration acceleration significantly decreases from steel rails to tunnel walls, with different vibration frequencies observed at various locations: steel rails (200 Hz–1400 Hz), track beds, and tunnel walls (70 Hz–400 Hz). Cracks notably increase peak acceleration, vibration levels, peak frequency, and steel rail displacement but do not alter the overall vibration trends. Tunnel wall responses show the highest sensitivity to cracks, with a 300% increase in peak frequency, followed by track beds (100%) and steel rails (70%). Vibration levels under one-third octave band processing increased by 12.4% for tunnel walls, 8.8% for track beds, and 2.2% for steel rails. Cracks also caused steel rails’ vertical and lateral displacement to rise by 112% and 53%, respectively. These findings provide valuable insights for vibration reduction and crack repair in long-term subway operations.

Experimental investigation of machine vibration rate and machine sound level in MQL turning of AISI 1525 steel employing mango oil as lubricant

AbstractThe detrimental effects of mineral oil on the environment and machine shops have led to a surge in the usage of vegetable oil as cutting fluid. The most popular vegetable oil lubricants are edible, and they have a lot of potential to rival human consumption eventually. The study examined using mango oil, an inedible vegetable oil, as a lubricant during AISI 1525 steel turning with tungsten inserts. The best machining parameters were ultimately found using the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) after the experimental studies were analyzed using the Taguchi process. Surface and contour plots were employed to investigate how different cutting settings affected the rate of vibration and sound level of the machine. Mango kernel seed oil outperformed its mineral oil counterparts by 2.3% and 57.7%, respectively, in terms of machine vibration rate and machine sound level. Moreover, feed rate (0.10 mm/rev), depth of cut (0.75 mm), and spindle speed (350 rev/min) are the ideal cutting settings to reduce machine vibrations and sound intensity. Mango oil holds significant potential as a substitute for cutting fluid derived from petroleum. The significance of this research is to formulate lubricants for industrial use that are more ecologically friendly and sustainable.

Validity of an expert-based job exposure matrix of hand-wrist physical exposures and their prospective associations with carpal tunnel syndrome.

Epidemiological studies of occupational risk factors for rare disorders require large study populations with adequate exposure estimates. Job exposure matrices (JEMs) linked to national information on standardized job titles may enable such large studies. We aimed to establish and validate a JEM for occupational hand-wrist exposures that could be linked to Danish national register data on job titles and hand-wrist disorders. We developed a JEM for hand-wrist repetition, force, vibration, and computer work in 96 job groups covering 91% of the 2227 occupational titles in the Danish version of the International Standard Classification of Occupation-88, and examined inter-rater reliability of five expert ratings. Poisson regression models were used to estimate incidence rate ratios for the association of carpal tunnel syndrome (CTS) with the level of repetitive movements, force, vibration, and hours of computer work described by the JEM, adjusted for relevant confounders. The JEM based on expert ratings had fair to good interrater reliability. The incidence of CTS increased with increasing levels of force, hand-wrist repetition, and vibration, Exposure-response patterns for repetition and vibration became less consistent after adjustment for force. The interaction between repetition and force was complex and did not support an overall positive interaction. Computer work was negatively associated with incident CTS. The JEM was able to identify known risk factors for CTS consistent with current evidence, and provided further associations on exposure-response patterns, mutual exposure adjustment, and interaction effects between repetition and force. The reliability of expert assessments of hand-wrist physical exposures was fair to good.

Evaluation of wear and friction properties of graphite modified Lubri polylactic acid with various infill fabricated by additive manufacturing techniques

AbstractThree‐dimension (3D) printing technology, also known as additive manufacturing, is a manufacturing technology that creates three‐dimensional objects by depositing material layer by layer, as opposed to subtractive manufacturing methods. However, the newness of the technology brings with it many unknowns. In particular, the raw materials used are constantly increasing. For this reason, testing each raw material used in many aspects and to determine the optimum production conditions is important for the wide use of 3D printing technology. These optimal conditions may be the parameters used to produce a material, and sometimes they can appear as a new material. In addition, the production of new materials with varying production parameters is fundamental research topic that requires comprehensive study. For all these purposes, in this study, a new material type known as Lubri PLA (LPLA) was selected and produced in different filling types and subjected to a series of friction and wear tests. Thus, it is aimed to determine the tribological properties of the material. Additionally, samples were produced in ten different infill types (grid, lines, triangels, hexagon, cubic, octal, zigzag, diagonal, diagonal 3D and gyroid) to show the effect of filler type on friction and wear behavior. These filler types were used for both PLA and Lubri PLA materials and a total of twenty samples were produced. Thereby, it is aimed to conduct a comprehensive study showing the effect of both material difference and filling type on friction‐wear behavior. Diameter deviations, hardness deviations, friction coefficient, temperature, specific wear rates (SWr), and vibration were selected as output parameters. According to the analysis of the test results, the best result in terms of material structure was given by Lubri PLA, while the best result in terms of filling type was obtained with Diagonal 3D filling type. In addition, the lowest vibration level was obtained in the LP‐Diagonal 3D sample with 0.041 mm/s2, while the highest vibration level was obtained in the P‐Grid sample with 1.756 mm/s2.Highlights LPLA closed to nominal value in diameter and hardness deviations Addition of graphite nanoparticle increased the dimensional accuracy Diagonal 3D infill type Lubri PLA composites showed the superior performance Graphite modified Lubri PLA composites demonstrated superior performance

Assessing the dredging vibrational effects on surrounding structures: The case of port nourishment in Bari

The paper presents a study on the dredging vibrational effects, for nourishment purpose, on the existing structures surrounding the worksite. Nourishment is a common operation when beach (or coasts, or ports) protection is required, allowing to reduce far-field impacts of coastal structures and improve navigability. Nourishment is then performed to reshape underwater land, and it is usually practiced by locating in the zones in which is required, soil coming from nearby areas. This latter is often obtained by a dredging process, in which the phases of excavation, transportation and soil placement are carried out. From the structural point of view, of interest is the excavation phase, which is usually performed in the water environment by a ship equipped with a dredge that mines the seabed, generating a new source of vibrations for the existing structures facing the working area. The aim of this paper is to assess the effects of vibrations induced by dredging operations, by taking as reference the recently performed nourishment in the port of Bari, Southern Italy. To this scope, an existing structure was selected and identified as sentry building, considering its extreme proximity to the worksite. Hence, a structural monitoring was performed, by investigating the behaviour of the structure before, during and after the dredging. Three main controls were carried out within the monitoring campaign: (a) check of the vibration levels and comparison with thresholds provided by the current Italian prescriptions for human comfort and structural damages; (b) operational modal analysis to assess the possible variations of the structural behaviour during dredging; (c) calibration of a numerical model to simulate the structural behaviour of the sentry building and to derive unknown geometrical and mechanical parameters. A full description of the reference building (characterized by a certain irregularity degree) and all the monitoring phases are reported throughout the manuscript. The results show that, over the monitoring period, the dredging vibration levels never exceeded the thresholds provided by code provisions, and subsequently, the sentry building did not report structural damages, as confirmed by the continuous control of dynamic parameters from experimental and numerical models. In addition, the contents of the paper show the paramount importance of the structural health monitoring, and the experience herein reported can inspire the management of buildings under particular actions like the ones herein investigated.

Rail pad damping characteristics in track vibration reduction evaluated through hammer tests and theoretical analysis

Although the majority of existing research addresses the stiffness characteristics of rail pads, the considerable impact of damping on vibration reduction underscores its significant research importance. In this study, the hammer test and theoretical calculation are both employed to assess the damping capacity across three rail pad types: prismatic (PRP), grooved (GRP), and mesh-type high-damping (MTHDRP). Through the hammer test, the MTHDRP notably surpassed GRP and PRP, achieving higher damping ratios by 51.40 % and 49.71 %, respectively, leading to significant vibration reductions in the track bed and rail. Comparison tests between three types of rail pads highlighted the enhanced performance of the MTHDRP, as it not only reduced vibration amplitudes and enhanced decay rates but also decreased vibration levels by 2−5 dB. Moreover, we established a refined finite element model of the fastener system and integrated it with the Logarithmic Decay Rate (LDR) method. Our findings demonstrate that this combination facilitates the calculation of the damping ratio of the rail pad. Furthermore, we conducted a comparative analysis between the LDR method and the envelope method, confirming its superior efficiency and reliability. Finally, the LDR method is used to predict the damping ratio of the rail pad with varying stiffness, showing that the softer the rail pad, the higher the corresponding damping ratio. Overall, our insights bridge the gap in theoretical calculations and experimental studies on rail pad damping characteristics, offering crucial guidance for rail pad selection in track vibration mitigation.

Quantum computation with electrons trapped on liquid Helium by using the centimeter-wave manipulating techniques

Surface-state electrons floating on liquid Helium have been served as one of the great potential experimental platforms to implement quantum computation, wherein the qubits are usually encoded by either the lowest two levels of the vertical vibrations (i.e., Hydrogen-like atoms) or the electronic spins. Given the relevant operations require additional techniques, such as the corresponding millimeter-wave or magnetic field manipulations, here we investigate how to implement the scalable quantum computation with a trapped electron array by alternatively using the usual centimeter-wave manipulating techniques. This is because the eigenfrequency of the present qubit, encoded by the two lowest levels of the lateral vibration of the trapped electron, is limited in the centimeter-wave band. We show that, by biasing the electrodes properly and driving the coplanar waveguide transmission line resonator, the electrons can be individually trapped in a series of anharmonic potentials on liquid Helium. Therefore, the well-developed circuit quantum electrodynamics technique for the implementation of superconducting quantum computation can be conveniently utilized here in the present quantum computing platform (proposed firstly in Phys Rev Lett 105:040503, 2010, to implement the fundamental logic gates, typically such as the single-qubit rotations of the individually addressable trapped electrons, the switchable two-qubit manipulations between the electrons trapped in the distant traps, and also the high-fidelity readouts of the target qubits. The feasibility of the proposal is also discussed by numerical simulations.

Active vibration control of gearbox housing using inertial mass actuators

Reducing carbon emissions is a primary goal in the global effort to combat climate change. Decreasing the weight of a vehicle improves efficiency and significantly reduces emissions. One of the main contributors to the vehicle’s weight is the gearbox. However, this approach presents a challenge as lightweight transmission systems experience higher vibrations and noise emission levels. In this paper, an economical active vibration control system is developed to control the vibration levels of an automotive gearbox housing. The gearbox’s mounting points are targeted to reduce the transmitted vibrations to the car cabin. The active control system aims to target high-frequency vibrations between 1000 Hz and 5000 Hz. A compact piezoelectric inertial mass actuator is designed and tested on a gearbox-constructed setup that simulates the vibrations and noise similar to a commercial automotive transmission system. The developed test-rig is excited by a piezo stack actuator at the input shaft. Filtered-x least mean square algorithm is implemented on a high-speed microcontroller, and the vibration levels are significantly reduced using the active system. An average reduction of approximately 8.5 dB is achieved between 1000 Hz and 1500 Hz, an average reduction of approximately 14 dB is obtained between 1500 and 2000 Hz, and an average reduction of 10.8 dB is attained between 2500 and 5000 Hz.

KANDINSKY ON COLORS AND THE VIRTUAL OBJECTLESS VIBRATIONS

If we accept that Kandinsky developed a systematic theory of the fundamentals of painting, we must ask what is the central concept underlying this attempt. This paper argues for the thesis that objectless vibration plays a central role in the reconstruction proposed Kandinsky’s first book, On the Spiritual in Art. This kind of vibration includes as a virtual field both shapes, sounds and colors. All these “fall” in an organized way from the virtual vibrations, and the purpose of abstract painting is to lift the mind beyond the specific distinctions of the visible world of objects to the abstract level of primordial vibrations. The article examines the origin, functions, and the effect this concept has on color theory.

Dynamic Response Analysis of a Subsea Rigid M-Shaped Jumper under Combined Internal and External Flows

To analyze the dynamic response of a rigid M-shaped jumper subjected to combined internal and external flows, a one-way coupled fluid–structure interaction process is applied. First, CFD simulations are conducted separately for the internal and external fluid domains. The pressure histories on the inner and outer walls are exported and loaded into the finite element model using inverse distance interpolation. Then, FEA is performed to determine the dynamic response, followed by a fatigue assessment based on the obtained stress data. The displacement, acceleration, and stress distribution along the M-shaped jumper are obtained. External flow velocity dominates the displacements, while internal flow velocity dominates the vibrations and stresses. The structural response to the combined effect of internal and external flows, plus the response to gravity alone, equals the sum of the structural responses to internal flow alone and external flow alone. Fatigue damage is calculated for the bend exhibiting the most intense vibration and higher stress levels, and the locations with significant damage correspond to areas with high maximum von Mises stress. This paper aims to evaluate multiple flow fields acting simultaneously on subsea pipelines and to identify the main factors that provide valuable information for their design, monitoring, and maintenance.

Effects of using different riveting tools on the vibration exposure and muscle fatigue of riveters and buckers

Riveters and Buckers in the aircraft manufacturing industry are exposed to high vibration levels, often exceeding the Daily Exposure Limit Value (DELV) of 5 m/s2. Proper control of vibration exposure and muscle fatigue is crucial to minimize the risk of Work-related Musculoskeletal Disorders (WMSD). This study investigates the impact of different rivet guns, gun handle positions, and bucking bars on vibration exposure and muscle fatigue. Ten male participants, evenly divided between riveters and buckers, participated in the experiment. Throughout the investigation, various data, including acceleration, Electromyography (EMG), heart rate, grip strength, and perceived level of exertion, were collected simultaneously from the participants. The findings revealed that gun types 3 and 4 resulted in 43.27% lower vibration exposure than gun types 1 and 2, while combining a spring dampener and tungsten bucking bar yielded 24.46% less vibration than steel and tungsten. For both riveters and buckers, the horizontal gun handle position reduced vibration by 12.66% compared to the vertical handle position. Consequently, it is crucial to consider the type of gun, bucking bar, and handle position to mitigate vibration exposure and muscle fatigue among riveters and buckers in the aircraft manufacturing industry.

Evaluation of ride quality in a passenger car with non-uniform tyre radial stiffness

This study is dedicated to examining the influence of varying radial stiffness along the circumference of tyres on a road vehicle ride quality and with a specific focus on aspects relevant to maintenance. Computer simulations employing a three-dimensional road-vehicle model, developed within commercial multi-body software, were conducted to explore the multifaceted factors influencing vehicle behaviour. These factors encompass road unevenness, driving speed, and the range of radial force variation resulting from harmonic changes in tire radial stiffness. Furthermore, simulation tests were carried out using a model of a diagnostic wheel balancing machine, which holds significance in vehicle maintenance practices. Measurements obtained from a passenger car equipped with standard tires with minimal non-uniformity, served as reference values for assessing the car's vibration levels. Additionally, selected scenarios were examined, involving vehicle with multiple wheels exhibiting non-uniform radial stiffness. The findings underscore that non-uniform radial stiffness can magnify the detrimental effects of road irregularities, potentially leading to amplified vibration levels and a heightened need for maintenance considerations.

Vibration Characteristics and Mesoscopic State Evolution of Ballasted Track During Dynamic Stabilizing Operation

Dynamic stabilization of large machines is necessary procedures before the commencement of operations railway lines that are newly built. However, limited or no studies have been carried out to reveal the operational mechanism from the vibration transfer characteristics of ballasted track subjected to excitation by stabilizing machines. The focus of this study is to solve this shortcoming. First, a typical new railway line was selected to test the dynamic response of the ballasted track during stabilizing operation, and then a stabilizing machine-ballasted track model was established with the help of the DEM-MBD coupling method. And the biaxial vibration accelerometers were inserted at various locations in the ballast bed to monitor the evolution of the vibration level on real-time basis. The influence of the stabilizing operation process on the vibration transmission and attenuation characteristics of sleeper and ballast bed was explored using wavelet analysis and Fast Fourier Transform method. The vibration absorption capacity and energy dissipation characteristics of the ballasted track under various stabilizing frequencies were analyzed. At the same time, the contact state and movement posture of ballast particles during the stabilizing operation were explored. Results showed that the vertical vibration attenuation rate of the slope toe of the ballast bed after the first stabilizing machine pass is 92.32%, while the vertical vibration attenuation rate of the second stabilizing machine is reduced by 3.14%. The second stabilizing machine can cause a large lateral movement of the ballast at the bottom of the sleeper. Under the excitation of 25[Formula: see text]Hz stabilizing frequency, it was observed that, the vibration absorption capacity of the ballast bed at the bottom of the sleeper is high, the vibration level at the ballast bed slope is low, and the stability is better. This is the optimal frequency for the stable operation of the new railway. This study can provide theoretical support for the establishment of the internal correlation mechanism between the vibration characteristics of stabilizing machines and the mechanical state of the ballast bed.

Theoretical and experimental investigations on a data-driven trajectory planning scheme for dynamic shape control of piezo-actuated compliant morphing structures

Piezo-actuated compliant morphing structures can transmit motion and force via elastic deformation with lower weight, simplified design, and higher accuracy, a typical example is the variable camber wing. However, the rapid shape change of compliant structures is a challenging control problem because it often results in a high level of vibration due to the structural flexibility necessary to achieve the morphing requirement. This study presents a model-free data-driven trajectory planning approach based on spline curves and surrogate-based optimization (SBO) to obtain smooth “rest-to-rest” morphing trajectories. The macro-fiber composite (MFC) patches are used for piezoelectric actuators to generate elastic deformation. The flexible beam and variable camber wing are used for both linear numerical simulation and experimental tests with various nonlinearities and uncertainties. An optimization criterion is proposed to minimize both transient and residual vibrations during the “rest-to-rest” motion. An extraordinarily terminal displacement error function is added to eliminate the effects of the hysteresis and creep of the actuator. The control inputs, i.e., voltage profiles for the MFCs, are defined using cubic spline curves via only a few control points. Then, the optimization problem is solved by employing a Kriging surrogate model-based algorithm integrated with the expected improvement (EI) infilling-sampling criterion, which constructs an efficient algorithm similar to reinforcement learning. The optimal morphing trajectories can be highly efficiently obtained by using only 4 control points and less than 150 samplings. The experimental results of both the plate model and the variable camber wing model show that the proposed method can not only achieve a smooth dynamic morphing trajectory with minimized vibration but also automatically compensate for hysteresis and creep. The proposed method provides an effective means for the rapid realization of an optimized morphing trajectory for compliant morphing structures.

Vibration transfer from underground train to multi-story building: Modelling and validation with in-situ test data

Excessive underground train-induced vibration becomes a serious environmental problem in cities. To investigate the vibration transfer from an underground train to a building nearby, an explicit-integration time-domain, three-dimensional finite element model is developed. The underground train, track, tunnel, soil layers and a typical multi-story building nearby are all fully coupled in this model. The complex geometries involving the track components and the building are all modelled in detail, which makes the simulation of vibration transfer more realistic from the underground train to the building. The model is validated with in-situ tests data and good agreements have been achieved between the numerical results and the experimental results both in time domain and frequency domain. The proposed model is applied to investigate the vibration transfer along the floors in the building and the influences of the soil stiffness on the vibration characteristics of the track-tunnel-soil-building system. It is found that the building vibration induced by an underground train is dominant at the frequency determined by the P2 resonance and influenced by the vibration modes of the building. The vertical vibration in the building decreases in a fluctuant pattern from the foundation to the top floor due to loss of high frequency contents and local modes. The vibration levels in different rooms at a same floor can be different due to the different local stiffness. A room with larger space thus smaller local stiffness usually has higher vibration level. Softer soil layers make the tunnel lining and the building have more low frequency vibration. The influence of the soil stiffness on the amplification scale along the floors of the building is found to be nonlinear and frequency-dependent, which needs to be further investigated.

Commuter Experience: An Assessment of Metro-Train Comfort Amidst Operational Vibroacoustic Conditions

This study investigates the impact of different passenger rolling stock structures and train configurations on vibrations and noise generated during operation. Vibroacoustic measurements were performed during acceleration, constant speed, and braking phases to analyze the effects using statistical analysis according to the relevant standards, revealing a statistically significant relationship between the equivalent noise level and vibration dose. In the context of the expanding Warsaw metro network, which is adding new lines and modern rolling stock, trends in the development of metro rolling stock were analyzed using five different types of metro vehicles, from the oldest to the newest designs. Vehicle performance was ranked in the context of ride comfort using standards and combined vibration and noise measures. The research results allowed for a collective comparative assessment of the construction of individual types of passenger rolling stock in terms of vibroacoustic phenomena, thanks to which it is possible to assess the impact of modern solutions and the justification for investing in modern rolling stock. Newer trains generally record significantly lower vibration and noise levels. The difference between the oldest and the most modern vehicle types is 57% for the vibration acceleration level (0.08 ms−2 RMS) and 66% for the noise level (2.2 dB LAeq).

Weibull distribution as a criterion of emergency levels

In the exploitation of machinery and equipment, one of the most important parameters is the dynamic state of the object. Observing residual processes is the most popular method of assessing the dynamic state. In particular, dynamic residual processes are a carrier of diagnostic information. Measuring the vibrations and noise of working mini-mining machines provides knowledge about the dynamics of the assessed machinery. Many years of knowledge and experience have allowed for the creation of diagnostic procedures. Within most machines used in the industry, the procedures considered standard allow for an effective diagnostic assessment and optimal management of mini-mining machine exploitation. The applicability of these standards is quite wide. However, there are machines with parameters that prevent the application of said standards. Mini-mining machines used in subterranean mining are one of these machines. In the case of diagnostic assessment of continuous miners, chain conveyors, as well as other machinery used in the technological chain, the usage of assessment brackets consistent with adopted standards is incorrect. In the diagnostic assessment of these types of mini-mining machines, an analysis of long-term trends is often used. The determination of acceptable vibration levels is obtained heuristically through observations of the damage up to the state of emergency. In the article, methods of mini mining machines state assessment using models of machine degradation, using Weibull distribution, are presented. The presented method has been used in real results of vibration measurement of underground machinery used in a coal mine. The analyses showed a large effectiveness of the presented method.

Comparison of train noise and vibration measurements with U.S. Department of Transportation model predictions

Wayside noise and ground-borne vibration measurements of freight and light rail train operations were carried out in Denver, CO in support of the Burnham Yard Transportation Planning Study being pursued by the Colorado Department of Transportation (CDOT). This study was intended to evaluate various track layout alternatives for the Consolidated Main Line (CML) freight railroad alignment and enhancement of Regional Transportation District (RTD) light rail operations while maintaining options for Front Range Passenger Rail (FRPR) within Burnham Yard and the surrounding areas. The objective of the measurements was to compare measured train noise and vibration levels with predictions using models sanctioned by the U.S. Department of Transportation (USDOT) in order to validate the use of these models to assess the noise and vibration impacts of the project alternatives. The models included the Federal Railroad Administration (FRA) Chicago Rail Efficiency And Transportation Efficiency (CREATE) freight noise model, the FRA Horn Noise Model, and the models included in the Federal Transit Administration (FTA) Transit Noise and Vibration Impact Assessment Manual. Based on a comparison of measured and modeled results, it was concluded that the USDOT models could be used to assess noise and vibration from train operations in the Burnham Yard Study Area.

Airborne acoustic assessment of impact-resistant fitness flooring systems

Fitness facilities in residential and mixed-used commercial buildings introduce important acoustic design challenges that must be considered in a building. Cardio activities such as running on treadmills, group classes for high intensity training, and weight training areas introduce high levels of unwanted noise and vibration into a building structure. Isolated floor constructions are generally coordinated and implemented during design but are not practical when buildings are completed and occupied. Impact-resistant fitness flooring systems are typically explored and installed as an alternate approach to reduce the transmission of impact noise and vibration. Non-standardized field airborne noise measurements of weight drops were conducted on an existing gym and on four possible impact-resistant fitness flooring upgrades to assess the reduction of impact noise levels in the offices located below the gym. The measurements were also compared to the HVAC background noise levels to observe the increase above background conditions and provide a subjective evaluation. The results of the measurements show that impact-resistant fitness flooring systems provide a noticeable reduction of impact noise, compared to standard fitness flooring systems. The results also show that impact-resistant fitness flooring systems that include specialty engineered shock pads as a base layer provide a significant reduction of impact noise levels.

Pickleball sounds: impact induced vibration and radiated sound

The rapid growth in popularity of pickleball and the ever-increasing number of pickleball courts has resulted in growing concerns about the effect of pickleball sounds on nearby neighbors. The vibration of the ball and paddle that is generated at impact, and which is the source of the radiated sound, was measured for different paddles as a function of frequency using an impact hammer instrumented with a force gage. Average vibration velocities over the paddle surface were generated that scale the radiated sound. Animations of paddle vibration were also generated. A paddles vibration level depends on its internal mechanical damping which was also measured. A performance metric is proposed where the paddles' sound levels are compared at the same "power" in terms of the change in momentum (velocity) of the pickleball on impact. Outdoor directivity measurements of the sound for a paddle were "dipole-like" in character with lower levels, by 10 dB or more, in the plane of the paddle compared to levels perpendicular to its face. The orientation of the courts may be important if the sound levels during play are quieter in the general direction along the nets.