Rattle Noise Research Articles

Impact of reduced sonic boom exposure on psychophysical and cognitive performance for simulated booms presented in a realistic indoor environment

This study aimed to quantify, in situations representative of the daily life of European citizens, the effects of sonic boom exposure on human responses, in the case of a new generation of supersonic commercial aircraft that should emit a reduced (compared to the past generation like Concorde) but perceivable boom while flying overland. Two reduced boom simulators were affixed to the bedrooms’ windows of a house located on our university campus. The simulators were used to study indoor the participants’ responses to realistic “outdoor” booms. Testing took place in both the living room and kitchen because the booms caused different intensities of rattle noise in those two rooms. Participants performed various tasks (communication, working memory, drawing, valence evaluation), took three mandatory rests and filled in various questionnaires about the annoyance caused by the booms and their mood. This paper focuses on the psychophysical and cognitive performance results. The booms resulted in delayed responses in the working memory task and in the valence evaluation task, and in a momentary slowing down in the drawing task. There was no significant effect in the communication task, even though a trend for a worsening of communication efficiency was observed. Taken together, the results suggest that reduced booms can interfere with cognitive and motor tasks by capturing attention, which can momentarily divert cognitive resources away from the task at hand. These results suggest future research directions and may lead to recommendations for future sonic boom regulations.

Analysis of the noise mechanism and interactions of torsional decoupling devices in the belt driven 48V mild hybrid powertrain

This paper analyzed the mechanism of rattle noise from a decoupling damper pulley in a 48V belt driven mild hybrid powertrain with a three-cylinder turbo engine. To decouple the 48V belt drive from the high engine torque fluctuation of the engine, a decoupling device at the front end of engine is employed, which interacts with the rear end decoupling device and results in the rattling issue. In this study as opposed to the conventional engine torsional vibration studies which neglect the low inertia belt drive, the effective inertia of 48V belt drive is considered in 1D, 3D torsional vibration analyses of the entire powertrain as it easily reaches up to 20% of the whole torsional inertia. In this way, the impact inside the crank torque fluctuation decoupler was identified as the source of the rattle noise, which verified in the experiments. The interaction of the front end belt drive and the various types of rear end flywheel is also analyzed through parametric studies.

Squeak and rattle noise prediction in vehicle acoustics

AbstractSqueak and rattle belong to unintended noise audible by occupants of a vehicle. This noise negatively affects the perceived built quality, leading to nonbuying decisions, high warranty costs, and poor brand reputation. Therefore, vehicle manufacturers seek to prevent the emergence of such noise, preferably in the early development phase and during production at the latest. This causes substantial monetary and temporal expenditure, which must be minimized. Rattle is defined as repeated impact. The underlying physical phenomenon is impulsive short‐duration contact normal to the surface. Squeak, in contrast, originates from an in‐contact motion in the tangential direction and is a friction‐induced stick‐slip phenomenon. State‐of‐the‐art numerical squeak and rattle prediction is based on linear analysis resulting in an empirical noise risk index. However, quantification of noise and assessment of audibility is not possible. The reason is the nonlinearity of the contact forces. Hence, the actual system response is not calculable with a linear approach. Mathematically, the nature of both excitation events is nonlinear due to frictional contact and nonsmooth due to short impulsive behavior in time. This makes linear simplification and a solution process in the time domain challenging. Both events appear periodically, leading to an oscillation characterized by fundamental and higher harmonics. Due to this periodic character, squeak and rattle phenomena fulfill the prerequisite for applying the harmonic balance method (HBM) to solve the governing nonlinear equation of motion. The more harmonics considered, the more precise the modeling and the dynamic response prediction. In addition, the alternating frequency/time domain method (AFT) allows for switching between the frequency and the time domain during the iterative solution process. Thus, the nonlinear contact forces can be evaluated in the time domain. The equation‐solving process results in the calculation of surface velocities. This gives way to determining a proxy for the emitted sound power of the oscillatory system. The simulation method based on combining HBM and AFT was validated on test rigs for squeak and rattle noise. The industrial applicability of this simulation approach was demonstrated numerically and experimentally on an actual vehicle part showing promising results. Thereby, important steps in nonlinear structural dynamics and vehicle acoustics were made toward a calm, smooth, and enjoyable ride for vehicle occupants.

Random Vibration and Noise Analysis of Vehicle Seat Using Numerical Method

The development of vehicle seat used is a challenging task for the automotive industry. In this research the safeness of automotive seats by structural analysis and a random vibration analysis were studied. Hence, the main objective of this study is to determine the suitable vehicle seat configuration based on Noise, Vibration, and Harshness (NVH) performance. In order to achieve this objective, CFD software which is ANSYS was used to analyse frequency and deformation using different force distributed and different material on seat vehicle structure which the force applied from 250 N until 1000 N. The material used is aluminium alloy, magnesium alloy and structural steel to analyse the strength of seat structure. At the end of the study, the effect of different types of material vehicle seat structure was studied. The results confirm that by changing the seat structure material, the rattle noise and in general BSR noise can be improved or controlled accordingly. Consequently, for the seat system which has an identifiable structural dynamic, the BSR noise can be managed and controlled in early design phase by using the seat CAE model.

Prediction of rattle noise in steering gear system and analysis of contributing factors through neural networks using design and manufacturing data

In a vehicle, rattle noise may occur when driving on bumpy roads due to clearance between parts of steering gear systems. The rattle noise is perceived by the drivers' ears and it can be the cause of a repair campaign. In order to reduce rattle noise, the dimensions of clearance between parts are optimally designed. Also, in the development stage, general auto parts companies manage rattle noise below a certain level. However, it is impossible to measure noise for all products at the production stage due to cost and time issues. In this paper, the noise prediction model using the neural network model for all products based on design factors and the data of manufacturing execution system was introduced. In addition, the main factors contributing to rattle noise were analyzed in the process of creating the model. By referring to the main factors contributing to noise, it helps in the design of the steering gear to reduce the rattle noise value.

Experimental investigation of gear rattle and nonlinear dynamic interaction in a dual-clutch transmission

Dual-clutch transmissions (DCT) having high efficiency and powershift are widely used in passenger cars thanks to the dual-clutch and preselection strategies. However, the dual-clutch transmission gear rattle behaviour still needs to be fully discovered, especially the influence caused by different preselection strategies. In this regard, the gear rattle sensitivity and dynamic evolution of the geartrain in a DCT were experimentally investigated on a rattle test bench and vehicle powertrain. The rattle response and instantaneous speed of all speed gears potentially contributing to the overall rattle are measured. The measured results from the DCT were compared with a similar structure six-speed manual transmission to depict its characteristics. Moreover, a multi-degree-of-freedom nonlinear torsional model was established to gain the nonlinear dynamic response along with the rising torsional irregularities; the model considers the crucial parameters affecting rattle behaviour. Two qualitative criteria were consequently given based on the numerical results and the law of the gear motion.The experimental results on the rattle test bench show that the DCT rattle behaviour varies with different preselected gears and is quite different from the manual transmission. The rattle sensitivity curves disclose an abrupt jump-up phenomenon when the excitation level reaches a certain level. The nominal input speed, preselection gear and lay-shaft configuration considerably determine the excitation level and amplitude increase of the jump-up on the rattle response. Based on the proposed qualitative criteria, a strongly nonlinear dynamic response is observed in the loaded gear pair under preselection conditions and deteriorates the rattle noise. A considerable dynamic interaction between active and passive sub-gearboxes is found. The appearance of the harmonics of the excitation frequency on the active input shaft that generates the high impact amplitude and density contributes to the jump-up and high vibration response on the rattle sensitivity. Finally, vehicle experiments reproduce the rattle jump-up and dynamic torsional interaction in the DCT powertrain are confirmed.

An experimental and theoretical investigation of the influence of backlash on gear train vibro-impacts and rattle noise

Rattling is a perennial gear noise problem observed in various powertrain components ranging from manual transmissions to engine balancers and timing gear trains. Under lightly loaded conditions, gear systems that are subjected to input and/or output torque fluctuations exhibit vibro-impacts as tooth separations and coast-side contacts take place in the presence of backlash. Experimental set-ups that can impose tightly controlled torque fluctuations to single or multi-mesh gear train are used here to determine the sensitivity of the rattling noise levels to the magnitudes of backlash within wide ranges of torque fluctuation parameters. Torsional discrete models of the experimental set-ups were used to simulate these rattling motions and to predict impact velocity-based rattle severity indexes as a function of both excitation parameters and backlash magnitudes. Single-mesh results show that the larger backlash values result in higher noise levels in most of the cases. In case of double-mesh systems, the resultant noise levels and the corresponding rattle indices exhibit different sensitivities to backlash magnitudes depending on the excitation conditions.

A Rattle Noise Severity Index for Multi-Mesh Gear Trains Subjected to Torque Fluctuations

AbstractExternal fluctuation torques acting on gear trains having clearances often cause vibro-impact motions with resultant rattle noise issues. In this study, an impact velocity-based rattle severity parameter that correlates with the resultant rattling noise is proposed for multimesh gear trains. An experimental setup is employed to measure torsional vibro-impact motions and the corresponding sound pressure levels of a three-axis gear train under various torque fluctuation conditions. A discrete torsional model of the experimental setup is developed and validated through comparisons to the vibration measurements. An impact velocity-based rattle severity index defined from the predicted response is proposed and shown to correlate well with the measured rattle noise sound pressure levels within a wide range of operating conditions. The demonstrated ability of the proposed rattle severity index in tracking rattle noise allows for the assessment of rattle consequences of a multimesh drivetrain solely from its predicted torsional response.

Feasibility study of single-mass flywheels with centrifugal pendulum vibration absorbers in vehicles with dual-clutch transmissions

Dual-clutch transmissions (DCTs) are very sensitive to torsional vibration and easily produce rattle noise if a single-mass flywheel (SMF) with a conventional torsional damper or a dual-mass flywheel (DMFW) is used in the vehicle. Only a DMFW combined with a centrifugal pendulum vibration absorber (CPVA) can eliminate rattle problem; however, this solution is expensive. Alternatively, a SMF with a CPVA is proposed to eliminate the DCT rattle issue, which could be a feasible and cost-effective solution free of side effects introduced by DMFWs. The vibration absorption principle of different types of pendulums and the rotor dynamic model are investigated to study the feasibility of a SMF with CPVA in a DCT vehicle. A seven-degree-of-freedom nonlinear lumped torsional vibration model is proposed to evaluate the torsional vibration attenuation performance of different configurations of torsional dampers and CPVAs. As per the model calculation results, the bifilar pendulum features the best attenuation performance compared with the circular and cycloid pendulums. The effect of pendulum parameters on attenuation is studied, and the optimized values are obtained. The SMF and optimized bifilar CPVA combination can satisfy the no-rattle requirements in vehicle relative to the DCT in-vehicle no-rattle threshold. A vehicle assessment on roads using physical pendulum prototypes indicates that the SMF with CPVA can be used as an alternative, cost-effective solution for DCTs, instead of the expensive DMFW with CPVA solution.

Dynamic behavior of an agricultural power take-off driveline for rattle noise reduction: Part 2. Experimental analysis of rattle noise effect according to spline tolerance level

Agricultural tractors comprise power take-off (PTO) drivelines, which that transmits engine power to the outside for various agricultural work, and various mechanical components are connected by spline couplings with tolerances. Dynamic behavior of the spline couplings causes a jumping phenomenon where the rotation speed fluctuation amplifies and then rapidly decreases. This paper experimentally examined the effects of spline tolerance on the dynamic behavior and PTO gear rattle noise for four different spline tolerance levels. For the fit tolerance (0.1 mm), no jumping was observed. For increasing tolerance levels of 0.5, 0.9, and 1.3 mm, the jumping rotation speed decreased to 920, 890, and 880 rpm, respectively. With increasing tolerance, both the rotation speed fluctuation and noise level immediately before jumping increased gradually. Furthermore, for the specimen with tolerance levels of 1.3 mm(type D), a transient range was observed in which the dynamic behaviors before and after jumping were mixed and rotation speed fluctuation and sound pressure level showed large deviations from their respective average values.

Squeak and Rattle recognition based on speaker recognition

Squeak and Rattle problems seriously affect the quality of the vehicles. In the adjustment stage of the automobile development process, engineers mainly rely on subjective evaluation to diagnose squeak and rattle noises, which is prone to misjudgment, missed judgment and time-consuming problems. There are gaps in relevant objective evaluation methods. This article proposed that speaker identification is used to identify squeak and rattle noises from the audio recorded in the test, to achieve objective and accurate results. In this paper, four kinds of squeak and rattle noise audios are used as samples, Mel Frequency Cepstrum Coefficient is extracted as feature vector to construct target Gaussian mixture models (GMM). The expectation, variance and correlation coefficient of the Gaussian mixture model can be calculated to describe the difference of multiple squeak and rattle noises. Using samples to judge accuracy rate, the results indicated that the acceptance accuracy rate reaches 100 %, and the rejection accuracy rate reaches more than 95 %.

Diagnosis and analysis of electric power steering rattle noise based on multiple coherence method

Electric power steering (EPS) system is becoming the primary source of Electric Vehicle (EV) noise due to absence of classic power train. The rattle noise produced by EPS, which is easily discernible when driving. Since the conventional subjective evaluation approach makes it difficult to identify the source, it is required to establish an objective way to solve such an issue. In this paper, the principle of multiple coherence method is first addressed analytically, and then is employed to analyze the vibration signal acquisition from EPS different points, meanwhile, combine with in-car sound signal, to accurately identify the specific location.

Experimental and Theoretical Investigation of Vibro-impact Motions of a Gear Pair Subjected to Torque Fluctuations to Define a Rattle Noise Severity Index

Abstract Vibro-impacts are common in various automotive engine and transmission gear applications. They are known to cause excessive noise levels, often called rattling or hammering. Input and output fluctuations acting on such systems cause tooth separations and sequences of impacts allowed by backlash at the gear mesh interfaces. The fluctuations leading gear rattling have often been studied for specific applications with the excitations produced typically by an internal combustion engine. As such, rattle evaluations have been often empirical and specific to the systems considered. In this study, an experimental test setup of a gear pair is developed to emulate the same torque fluctuations in a laboratory environment. This setup is used to establish an impact velocity-based rattle severity index defined by the measured torsional behavior of the drive train that is shown to correlate well with the measured sound pressure levels. With that, a validated dynamic model of the experimental setup is employed to predict the same index to allow estimation of rattle noise outcome solely from a torsional dynamic model of the drivetrain. Predicted rattle severity indexes are shown to agree well with the measured ones within wide ranges of torque fluctuations and backlash magnitudes, allowing an assessment of rattle performance of a drivetrain solely from a torsional model.

Development of dynamic behavior model for damping characteristics of suspension for automobiles

The suspension for automobiles reduces the vibrations transmitted from the road surface to the vehicle body, which improves vehicle dynamic performance and ride comfort, springs to the shock absorber as the main structure, and oil damper is widely employed in the vibration damping portion. In recent years, in response to the problem of reducing the noise in the car which is called rattle noise, evaluation is required including transient attenuation characteristics of the damper. We construct a damping force characteristic analysis model which considers the transient response of a damper in the car noise prediction system using the 1D model, and the evaluation of transient damping force response near the open operation using this model was obtained.

Root cause analysis of rattle noise in twin-tube vehicle dampers

The aim of this work is to provide an insight into the rattle noise phenomena occurring in double-tube (twin-tube) vehicle suspension dampers. In the dampers the particular phenomenon results from interactions between the valve(s) and the fluid passing through them. The rattling noise phenomena is known to degrade the vehicle passenger’s perception of ride comfort as well as to influence the performance of the dampers at low and medium speeds in particular. In the paper the authors reveal the results of a DOE (Design of Experiment) study involving several design parameters known to affect rattling occurrence. By running a series of purpose-designed tests the authors investigate not only the contribution of each particular parameter but the interactions between them. The results are presented in the form of pareto charts, main effect plots as well as interaction plots. It is expected the outcome of the analysis will aid in a better comprehension of the phenomena as well the definition of valve configurations to minimize their performance degradation.

Quantitative prediction of rattle noise: An experimentally validated approach using the harmonic balance method

Rattle noise in a car’s interior must be avoided to prevent customer complaints. Virtually predicting such disturbing sounds without expensive prototyping has become more important in recent years to reduce development costs. For this reason, methods for simulating the acoustic behavior of rattling systems are gaining attention. This research validates the harmonic balance method for a quantitative prediction of rattle noise. For this purpose, a test rig is developed showing representative rattling and non-rattling configurations. The test rig consists of an oscillating beam-like structure with a lumped mass at its tip. When amplitudes are large enough, the beam serves as an impulsive excitation of a plastic plate. The nonlinear dynamic system response is measured using a 3D scanning laser Doppler vibrometer and the harmonic balance method is used to calculate the system’s response, which predicts the first and higher order harmonics with high degree of accuracy. Furthermore, measurements and simulations show that solutions for the system’s response are not necessarily unique for all predefined harmonic excitation frequencies. Finally, a motivation is given for why higher harmonics have to be taken into account to adequately predict the acoustic behavior.

Quantification of rattle noise generations from automotive compartments by variational mode decomposition

In this study, an assessment method is proposed to quantify rattle noise by applying variational mode decomposition (VMD) to automotive structural sound radiations. The complete prevention of rattle sounds in assembled plate structures excited by vehicle operation conditions is difficult. It is important to design automotive structures that induce minimal acoustic contributions to the vehicle interior noise. To investigate occurrence of unpredictable short-duration sounds, precise decomposition without distortion is required. The VMD has advantages on disintegration of complex signals. To confirm the decomposition performance for sounds, synthetic acoustic signals composed of pink and impact sounds were analyzed. The separation performance was compared to conventional spectral filtering methods and complete ensemble empirical mode decomposition (CEEMD). The sound radiation from an automotive structure was measured using the vibration test in an anechoic chamber. The measured sound was decomposed into background and rattle sounds using VMD. The broadband background sound was quantified by level. The rattle sound was evaluated using Prony analysis. To investigate the masking effect, just noticeable differences (JND) were obtained with variations in the levels of the decomposed sounds. The algorithm to derive annoyance index from evaluation of the decomposed sounds was proposed. Auditory experiments were conducted to obtain perceived annoyance of the noise emitted by an automotive structure. The annoyance index predicted the actual perception precisely compared with the objective sound quality metrics. The loudness alone did not effectively quantify the impact sound. The results were used to confirm the reliability of the proposed method, demonstrating the advantages of VMD on impact sound annoyance quantification analysis.

Localization of rattle noise sources in the vehicle underbody using acceleration signals

The buzz, squeak, and rattle (BSR) problem is one of the most important issues affecting vehicle satisfaction related to unexpected noise and vibration and has been attracting increased attention because of the rise of electric and hybrid vehicles. However, until recently, the vehicle underbody BSR has not been studied as extensively as the upper-body or interior BSR owing to a number of complex issues, such as the lack of suitable methods for measuring or visualizing the underbody BSR. This study proposes a method for localizing the rattle noise source in the vehicle underbody using the accelerations measured during a vehicle driving test. The acceleration signals are denoised by considering the characteristics of rattle; then, a series of rattle-induced impulse signal units included in the denoised acceleration signals are identified via machine learning at the level of BSR experts. Finally, the accelerometer closer to the rattle noise source is quantitatively determined by analyzing the correlation indexes in the frequency domain based on the properties of the rattle-induced impulse signal units, which depend on their relative position from the rattle noise source. The proposed method is based only on the accelerations measured from the driving test and the rattle signal transmission characteristics, and does not require complex vehicle dynamics analysis; therefore, it can be widely used regardless of the vehicle type at low cost.

An experimental methodology to study engine gear rattle problems

Gear induced noise represents a major part of overall automotive drivetrain noise. Gear rattle noise is caused by strongly nonlinear dynamic behavior of the gear pair, primarily due to external torque of speed fluctuations under lightly loaded conditions. Such loading conditions cannot be generated by using the conventional gear dynamics test set-ups that employ power recirculating gearbox arrangements or conventional electric motors. In this paper, a new test set-up is introduced to emulate the actual torque/velocity fluctuations of the input and/or output members of a gear train through three-phase synchronous servo-motors. In addition to establishing backlash boundaries, a pair of absolute encoders are used to measure the relative motions of the gears as well as their impacts along the drive and coast sides flanks or gears. Torsional vibratory behavior of a gear pair is presented at different backlash values under several input/output fluctuation conditions along with the companion sound pressure measurements.

Dynamic behavior of an agricultural power take-off driveline for rattle noise reduction: Part 1. Effect of spline tolerance on the power take-off rattle noise

An agricultural tractor has a power take-off (PTO) driveline that is directly connected to the engine to improve its power transmission efficiency. The PTO driveline comprises various mechanical components coupled by a spline joint. The spline coupling tolerance causes collisions between various mechanical parts of the PTO driveline and affects gear collision, thereby causing rattle noise. Therefore, the aim of this study is to conduct a dynamic behavior analysis to predict the gear rattle noise level of a PTO driveline. The dynamic behavior of the PTO driveline was analyzed through 1D simulations, and the results confirmed that the dynamic behavior changes according to rotation speed. Experimental verification of the dynamic behavior analysis results confirmed that the dynamic behavior changes as the main engine excitation-component amplification changes and then decreases at a relatively high rotation speed. Additionally, the dynamic behavior changes of the PTO driveline resulted in a jumping phenomenon that occurs rapidly at a specific rotation speed. The amplification of the engine’s main components was reduced from 3 to 4 times to 1.2 times owing to the jumping phenomenon; the noise level of the gear rattle was also reduced by approximately 10.9 dB(A).