Vehicle Noise and Vibration Refinement

Xu Wang

• Publisher: Woodhead Publishing
• Year: 2010
• ISBN:
  9781845698041
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

High standards of noise, vibration and harshness (NVH) performance are expected in vehicle design. Refinement is therefore one of the main engineering/design attributes to be addressed when developing new vehicle models and components.Vehicle noise and vibration refinement provides a review of noise and vibration refinement principles, methods, advanced experimental and modelling techniques and palliative treatments necessary in the process of vehicle design, development and integration in order to meet noise and vibration standards. Case studies from the collective experience of specialists working for major automotive companies are included to form an important reference for engineers practising in the motor industry who seek to overcome the technological challenges faced in developing quieter, more comfortable cars.The reader will be able to develop an in-depth knowledge of the source and transmission mechanisms of noise and vibration in motor vehicles, and a clear understanding of vehicle refinement issues that directly influence a customer's purchasing decision.

• Reviews noise and vibration refinement principles, methods and modelling techniques necessary in vehicle design, development and integration in order to meet noise and vibration standards
• Outlines objectives driving development and the significance of vehicle noise and vibration refinement whilst documenting definitions of key terms for use in practice
• Case studies demonstrate measurement and modelling in industry and illustrate key testing methods including hand sensing and environmental testing

Part I

Introduction

1

Rationale and history of vehicle noise and vibration refinement

X. Wang, RMIT University, Australia

Abstract:

Vehicle noise and vibration performance are important aspects of vehicle design validation criteria, and have significant influence on the overall image of a vehicle. This chapter summarizes the objectives and significance of vehicle noise and vibration refinement, defines its scope and illustrates its relationship to the vehicle development process. Some vehicle noise and vibration terms are defined and a brief history of motoring and vehicle refinement is presented.

Key words

noise

vibration

refinement

vehicle development process

target setting

benchmarking

design

development

testing

validation

audit

1.1 Introduction

Vehicle noise and vibration performance is an important vehicle design validation criterion, since it significantly affects the overall image of a vehicle. Noise and vibration degrade the driver’s and passengers’ comfort and induce stress, fatigue and feelings of insecurity. Modern vehicle development requires noise and vibration refinement to deliver the proper level of customer satisfaction and acceptance. It is common for a customer’s perception of vehicle quality to relate closely to the noise and vibration characteristics of the vehicle.

Globalization combined with increased competition in the marketplace requires a vehicle’s noise and vibration characteristics to be well optimized. The sound present in the interior of a vehicle consists mainly of powertrain noise, road noise and wind noise. Given the increased market demand for lighter and more powerful vehicles, it becomes evident that powertrain-induced noise is a key component of the vehicle’s interior noise. Automotive manufacturers are increasing the number of powertrains available on vehicle programs because of the potential for improved fuel economy. For example, diesel-powered vehicles are one of the popular alternatives in the global automotive market. This presents and further complicates a unique set of noise and vibration challenges that need to be solved during the vehicle development process. This means not only eliminating squeaks and rattles and suppressing overall noise levels, but also tuning the sound of t automobile to reflect the high quality and distinction of the brand.

1.2 Objectives and significance of vehicle noise and vibration refinement

Noise, vibration and harshness (NVH) have become increasingly important as a result of the demand for increasing refinement. Vibration has always been an important issue closely related to reliability and quality. Noise of increasing importance to vehicle users and environments. Harshness is related to the quality and transient nature of vibration and noise. Noise and vibration problems may originate from systems such as the engine pumps, drivetrain, wheels and tyres, or may be related to system integration issues, for example matching between powertrain and body and between chassis and body. Controlling vibration and noise in vehicles poses severe challenge to designers because motor vehicles have severe sources of vibration and noise which, being interrelated and speed dependent, are different from many machine systems. Vehicle noise a vibration refinement has been considered essential for vehicle design and development because of legislation, marketing needs and custom expectations. In order to minimize the impact of the automobile on t environment, legislation has become increasingly demanding on vehicle noise emission and vibration controls. Noise and vibration refinement distinguishes a vehicle from its competitors, thereby attracting new customers.

1.3 Scope of vehicle noise and vibration refinement

Vehicle refinement encompasses noise and vibration refinement, ride and driveability. Vehicle refinement affects the customer’s buying decision and the business of selling passenger cars, as it directly affects the driving experience. A refined vehicle should have the following characteristics:

• High ride quality

• Good driveability

• Low wind noise

• Low road noise

• Low engine noise

• Idle refinement (low noise and vibration)

• Cruising refinement (low noise and vibration, good ride quality)

• Low transmission noise

• Low levels of shake and vibration

• Low levels of rattles, squeaks and sizzles

• Low level of exterior noise of good quality

• Low level of interior noise of good quality

• Noise that is welcome as a ‘feature’.

Customers have come to expect continuous improvement in new vehicles. They expect their new purchase to be better equipped and more comfortable, and to perform better than the vehicle they have just traded in. If the new vehicle is better in all respects than the old one, but lacks refinement, the customer will not be fully satisfied. Vehicle refinement aims to enhance vehicle performance, styling and acoustics. The motivations for vehicle refinement are therefore:

• Brand image

• Drive comfort

• Quality enhancement

• Cost and weight reduction

• Customer satisfaction.

Noise and vibration refinement is an important aspect of vehicle refinement. It deals with noise and vibration suppression, noise and vibration design, rattle and squeak suppression. The vehicle noise and vibration refinement process covers the following tasks:

• Benchmarking

• Target setting

• Noise and vibration design and development

• Prototype NVH testing and design validation

• Noise and vibration diagnostics and problem solving

• NVH design solutions for production

• NVH audits on production vehicles.

1.4 The vehicle development process and vehicle noise and vibration refinement

Figure 1.1 shows the four-phase vehicle development process. T...