Noise, Vibration and Harshness (NVH) Research Papers (original) (raw)

Se presenta el diseño y desarrollo de banco NVH (Noise Vibration And Harshness), utilizado para evaluar el comportamiento y estado de las Flechas de velocidad Constante (FVC) mediante ruido, vibración y fuerza axial, manufacturadas en VelCon S.A de C.V. Se realiza un análisis de Paretos de problemas de rechazo interno y reclamo de cliente en VelCon y problemas más comunes generales presentados en FVC [1-10] como fuente, trasmisora y modificadora de ruido y vibración en el vehículo mediante el tren de transmisión y así definir la necesidad para determinar los requerimientos necesarios. Posteriormente se hace un análisis de bancos actuales de NVH o que trabajan bajo el mismo concepto para determinar los parámetros de mayor influencia que se presentan en el tren de transmisión en vehículo y reproducirlos idénticos o en escala.

This was a white paper submitted at my Ex-organisation on the noise control of vacuum cleaners

This paper presents a comparison of soft and hard
chopping on an 8/6 SRM in terms of noise, vibration and
harshness. Transient-state measurements are used to plot speedfrequency
signatures of current, vibration and acoustic noise of
the SRM for different load torques. With this technique speedrelated
frequencies can be distinguished from resonance
frequencies, and therefore, more information can be extracted
from the plots. The results show that hard chopping increases the
loudness of acoustic noise compared to soft chopping, with a
frequency shift to higher values. This however leads to an
attenuation of the vibration and noise amplitudes at the most
critical resonance of the SRM, situated at a relatively low
frequency.

- by Yves Mollet and +1
- •
- Electrical Engineering, Noise, Vibration and Harshness (NVH), SWITCHED RELUCTANCE MOTOR

The main aim of this proposal is to summarise the findings of previous technical reports and to investigate and propose improvements on deign to control the levels of noise generated by car tyres. The castor tyre can be a better idea to perform experiment. These wheels are available in this range are designed as per international quality standards and norms. It is available in various sizes and widths which can be use for study purposes or any other load bearing capacity. The result of this research and analysis will lead to further ideas of how to reduce the noise levels and these will be investigated.

Disc brake noise is recognized as a major problem of the
automotive industry. Various experimental and numerical
techniques have been developed to model the noisy brake and
investigate possible solutions. Developing a virtual model of
the disc brake which can accurately reproduce the behavior of
the brake unit under different conditions is a considerable step
forward towards reaching this goal.
Among various aspects of the analytical model of a disc brake,
application of the correct value of damping based on the
material properties and functional frequency range of each
component is a significant factor in ensuring correct prediction
of the brake system behavior.
Complex Eigenvalue Analysis is well established as a tool for
predicting brake instabilities which can potentially lead to
brake noise. However, it is known to over-predict instabilities
i.e. predict instabilities which do not occur in the real brake
system. The over-prediction of unstable modes is thought to be
as a result of insufficient damping in the model compared with
the real brake system. For this reason, the Finite Element
Analysis model of the brake unit needs to be tuned in terms of
damping characteristics to ensure that the model replicates the
system's real behavior.
This study aims to tune the damping of different components
of the brake unit Finite Element Analysis model using data
from an experimental study. The study then compares the
instability predictions of the tuned model and the un-damped
model, and correlates them with the behavior of the same
brake unit when tested on a dynamometer. This is intended to
minimize over-predicted instabilities.

NVH (Noise, Vibration and Harshness) is an important aspect of vehicle design since it is one of the biggest influencing factors for customer while making decision to buy a vehicle. Hence, automotive engineers strive to design superior cabin compartment to maintain pleasant levels of noise, vibration and the overall experience within the vehicle. Transfer function analysis is primarily used to quantify the relative relationship between source and receiver region. The focus of this paper is to measure vibro-acoustic transfer function using reciprocity approach instead of direct impact test measurement to evaluate the frequency response of heavy layer barrier materials. Normally, it is difficult to mount and quantify the correct response of such heavy damped materials in usual random incidence sound transmission test since its performance is very sensitive to leakage (less than 1% required). The purpose of demonstrating the vibro-acoustic reciprocity in a vehicle is to show that the principle works good even for non-linear system like vehicle, in most cases where mutual coupling effects are negligible and hence at most area the frequency response for tested material holds true even at vehicle level. The reciprocal measurement involves usage of dodecahedral sound source to acoustically excite the cabin from desired seating location and accelerometers being placed at all the response locations of interest on vehicle body. In case of direct measurement, vehicle body is excited using impact hammer and acoustic pressure is measured at desired seating location. It is observed that transfer function calculated with direct and reciprocal measurements showed a good match with overall deviation of less than 2 dB on an average. The reciprocal measurement based transfer function can be used as a logical input for prediction of receiver level sound pressure data/sound quality or prediction of source strength depending on the subject of requirement for dynamic tests. The validation helps in optimizing the traditional approach for measuring structural response using vibro-acoustic transfer function in frequency range of 80-5000 Hz. The traditional method involving impact hammer test for predicting response at various points in vehicles is a time taking process and inaccessible measurement locations are prone to error. The linearity of the reciprocity measurement is checked for various locations in vehicles and found to be working satisfactorily in frequency range of 80-5000 Hz where frequencies till 1000 Hz are very well correlated and deviations are observed above 1000 Hz comparatively for all measurement locations. The main idea of this paper is the application of above reciprocity principle for assessment of acoustic materials used for noise control. The reciprocal approach of predicting transfer function is used to capture frequency response of heavy layer barrier material which uniquely characterizes its behavior. To verify that material comparison holds true, comparison of two test samples with known performance are also made and it is seen to correctly quantify the frequency behaviour of one sample with respect to other.

- by Nitesh Anerao
- •
- Acoustics, vehicle NVH, Transfer Function, Noise, Vibration and Harshness (NVH)

Take-up judder is the first rigid body torsional mode of the clutch system, which occurs during clutch engagement. This phenomenon is induced by stick-slip oscillations at the friction lining interfaces between the clutch disc and flywheel, and the pressure plate. The phenomenon is influenced by the clutch lining friction characteristics, the topography of the mating-sliding surfaces and the operational conditions during the engagement process.
Therefore, the interfacial characteristics are affected by contact pressure, interfacial slip speed and surface temperature. Take-up judder causes driver and vehicle occupant discomfort, as well as gradual wear of contacting surfaces. The response frequency of the system is reported to be in the range 5-20Hz, depending on the clutch system and vehicle inertia. In this paper the measured interfacial friction characteristics together with clamp load variation (contact pressure) under different surface temperatures are included in a multidegree of freedom dynamic analysis to obtain torsional vibrations of the system, pertaining to take-up judder conditions. Such an in-depth investigation has not hitherto been reported in literature. The paper shows that take-up judder is omnipresent under all clutch engagement conditions, but its poignancy is most evident at cold surface temperatures. It is also shown that the transient judder response has a broader spectral content that is generally acknowledged.

- by Ramin Rahmani
- •
- Thermal Engineering, Vibrations, Power System, Tribology (Engineering)

Noise Vibration and Hardness are some of the most common problems and quality criteria in mobile automotive parts. This is the case of constant velocity joint of drive shaft. The test rig presented was develop to evaluate and characterize the drive shaft for vehicle front traction. It reproduce parameters as speed, angle and torque similar to those presented in normal operation. In the output it allows measurement of axial force and vibration. The design criteria and outline of system are presented. Then the development of the load cell for axial force and torque using strain gages. The design was based on flexion and torsion theories for stress analysis and deformations. The strain gages arrangement with the instrumentation are presented with de calibration procedure and its results. Design and instrumentation were verified at every stage of the process to achieve the required accuracy. Finally static and dynamic test was carried out and the theorical and experimental results consistent with 1.022\% for axial force and 1.72\% for torque of deviation.

- by Salvador Echeverría
- •
- Vibrations, Instrumentation, Noise, Noise, Vibration and Harshness (NVH)

Abstract – This study aims to understand the influence of the position of the centre of gravity of the powertrain in the engine suspension system. By changing the position of the engine baricentre in relation of the axis of minimal moment of inertia, alters the engine dynamics, influencing the preload of the torque restrictor, mounting filtering, steering wheel vibration and in the internal noise inside the vehicle. The computational and experimental results showed a significant worsening when the engine is moved forward the Torque Roll axle and unacceptable values when the engine is moved backwards this axle, thus confirming the importance of this premise.

Noise and vibrations emitted from the structure of a combustion engine has contributions due to combustion process, motion of parts, flow and exhaust etc. Combustion based noise has major contributions in noise emissions, hence it is important to analyze the combustion occurring inside the combustion chamber as well as overall structure of engine to improve performance of engines on various NVH benchmarks.
The presented work discusses a methodology that may be used for analysis of in-cylinder pressure development for a gasoline engine. Efficient monitoring of combustion process is a key for regulating emissions form engine as well as achieving fuel economy. Relevant cyclic events occurring during course of operation of engine were extracted and identified using a novel mean frequency method. The proposed methodology may be used for structural modification of engine to improve its performance on various NVH benchmarks.

Resumo – Este trabalho visa compreender a influência da posição do centro de gravidade do motor no sistema suspensão motopropulsora. Alterando-se a posição do baricentro do motopropulsor em relação ao eixo de mínima inércia do sistema, altera-se a dinâmica do motor, influenciando na pré-carga do restritor de torque, filtragem dos coxins, vibração no volante e no ruído no interior do veículo. Os resultados computacionais e experimentais mostraram uma piora significativa quando o motor é deslocado para frente do eixo Torque Roll e valores inaceitáveis quando deslocado para trás deste eixo, verificando assim a importância dessa premissa.

Lightly damped non-linear systems such as vehicular drivelines undergo a plethora of Noise, Vibration and Harshness (NVH) problems. The clonk phenomenon is one concern which occurs as the result of impulsive torque input in the form of sudden clutch actuation or throttle tip-in and back-out. The resulting impact of meshing gear pairs propagate structural waves down the driveline. With lightly damped thin-walled tubes having high modal density, elasto-acoustic coupling occurs. High frequency noise emission is of metallic nature and quite disconcerting to vehicle occupants as well as passers-by. It is perceived as structural failure and/or poor-quality build. Therefore, the occurrence of the phenomenon is a concern to vehicle manufacturers and progressively constitutes a warranty concern. This paper investigates the clonk phenomenon through use of a long-wheel base rear drive light truck test rig. The investigation uses psychoacoustic metrics to establish the severity of clonk noise in different maneuvers. This is an attempt to quantify the effect of transient clonk event which is usually ascertained through subjective evaluation ratings in a customer/jury clinic in industry. Alternatively, detailed numerical analysis is carried out with parametric studies to quantify different clonk events, a very time consuming approach which is not usually correlated with occupants' perception of the event. Therefore, the experimental NVH monitoring-psycho-acoustic approach is new for the case of clonk and not hitherto reported in literature. The study corroborates the results and conclusions of previous work, pointing to the loudness and sharpness of high frequency short-lived "metallic" response, which is attuned to human aural perception. The psychoacoustic analysis has shown this to be as the result of short duration hard impact (accelerative period). This hard impact duration accounts for the bulk loudness and sharpness of the overall event. Therefore, effective palliation should focus on the attenuation of particular frequency bands, which carry the main contribution to loudness and sharpness.

- by Ramin Rahmani
- •
- Acoustics, Psychoacoustics, Vehicle Dynamics, NVH