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Traditionally, powertrain sound quality targets have been set by making judgements about wide open throttle acceleration sounds played in a listening room. This paper describes a recent project in which fourteen target sounds were evaluated against twenty-six existing cars including competitors and current models, using the interactive NVH Simulator approach. It explains how a minimum data method, based on existing historical data, was used to create and validate a simulator model for each car which could be freely-driven but had a limited driving envelope. The study highlights the role of key programme decision makers and summarises the benefits offered by interactivity in the process of developing, evaluating and signing off vehicle sound quality targets.

A full vehicle NVH Simulator has been developed to provide a realistic interactive in-car environment where a subject can experience multi-modal stimuli ( accurately reproduced sound and vibration as well as visual ) whilst either driving or being driven. This paper describes its use in learning about the strategies subjects employ during sound evaluations, and how this information can help optimise decision making during product development. It is possible to understand how subjects assess the sound of vehicles, both in the way that they drive the vehicle and importantly which elements of the sound character have greatest influence on their evaluation of the vehicle. It is also possible to compare the strategies employed by NVH engineers, company decision-makers and non-experts such as customers.

One of the great challenges of the NVH development process is to ensure that customers and stakeholders in the vehicle team are involved in sound quality decision making throughout a new vehicle programme. Recent developments of interactive NVH simulators have enabled a cost-effective customer-focused method for capturing the opinions and decision making processes of people who are not NVH experts. This paper describes the latest enhancement to the NVH Simulator approach which allows the sounds of virtual vehicles to be evaluated whilst driving on-road. The sounds are created and presented to the driver in such a way that they appear totally natural and the assessor is not aware that they are synthesized. Since the subjective evaluations are performed on normal roads, key decision makers can understand, sign up with confidence to, and appreciate the value of the proposed sounds.

This paper describes the use of an interactive NVH simulator in simulating and designing the sound character of a vehicle with a multi-mode engine and active exhaust valve. When designing a vehicle for sound quality, it is not sufficient to merely record some discreet operating conditions and modify these in a traditional sound quality program. The ability to simulate the sound quality of the vehicle over the full operating envelope is a necessity. Additionally, the ability to break down the sound contributions from intake, exhaust and other key contributors to the driver's ear, and manipulate these independently is also essential. In the case described here, an additional factor makes it mandatory that an accurate vehicle sound simulation is performed. The state of the engine and exhaust contribution, and thus the sound of the vehicle, change based on several parameters - vehicle speed, load demand and gear.

The sound field in a vehicle is one of the most complex environments being a mixture of multiple, correlated and uncorrelated sound sources. The simulation of vehicle interior sound has traditionally been produced by combining multiple test results where the influence of one source is enhanced while the other sources are suppressed, such as towing the vehicle on a rough surface for road noise, or measuring noise in a wind tunnel. Such methods are costly and provide inherent inaccuracies due to source contamination and lack of synchronization between sources. In addition they preclude the addition of analytical predictions into the simulation. The authors propose an alternative approach in which the component sounds are decomposed or separated from a single operating measurement and which provide the basis for accurate sound synthesis.

Experiencing the results of virtual NVH analysis in an immersive physical simulation is the only accurate method of developing vehicle, system or component targets and designs. This paper describes an engineering approach specifically created to enable physical interaction with test, CAE and hybrid NVH models, at every stage in the vehicle design process from concept to full detail. It explains the need for sound and vibration decomposition and synthesis, and interactive sound and vibration replay. Implementation of this process has led to the development of engineering tools that enable Interactive NVH Simulation. The paper also describes the practical use an engineer can make of a ‘rapid prototyping’ desktop NVH simulator in the design process. A full scale NVH Simulator is then used to allow evaluation of final design alternatives under realistic driving conditions by non-specialists (i.e. the customer) as well as specialists.

Many electric (EV) and hybrid-electric (HEV) vehicles are designed to operate using only electric propulsion at low road speeds. This has resulted in significantly reduced vehicle noise levels in urban situations. Although this may be viewed by many as a benefit, a risk to safety exists for those who rely on the engine noise to help detect the presence, location and behaviour of a vehicle in their vicinity. In recognition of this, legislation is being introduced globally which will require automotive manufacturers to implement external warning sound systems. A key challenge for premium vehicle manufacturers is the development of a suitable warning sound signature which also conveys the appropriate brand aspirations for the product. A further major difficulty exists when trying to robustly evaluate potential exterior sounds by running large-scale trials in the real world.

As pressures mount to remove physical prototyping from the vehicle development process, there is a growing need for subjective evaluations of virtual prototypes. Virtually assessing NVH vehicle targets and using driving simulators to make those early critical design decisions is becoming a larger part of the NVH engineering process. Today this is only possible if you put a driving simulator at the center of your development process. Being able to drive and evaluate both test and simulation results simultaneously in a simulator allows engineering teams to leverage a hybrid engineering approach. By starting with measured on-road data from a physical vehicle, engineers can build virtual prototypes. By using this hybrid engineering process to incorporate CAE and test data together an engineer can create a virtual vehicle model with the desired NVH characteristics as a physical vehicle.

In a traditional NVH process it is not possible to experience the NVH of a new vehicle until physical prototypes have been built. An interactive NVH Simulator provides a means of evaluating the binaural sound and tactile point vibrations obtained from measurements, or CAE predictions, or a combination of both, much earlier in the design cycle. This paper describes how interactive evaluations are carried out in an NVH Simulator, illustrated by two recent applications of using it early in a new vehicle programme. In both examples engineers, attribute leaders and managers, who were not NVH experts, could be confidently involved in deciding which were the most appropriate target sounds, or which was the most cost effective design.

Computer modelling, virtual prototyping and simulation is widely used in the automotive industry to optimize the development process. While the use of CAE is widespread, on its own it lacks the ability to provide observable acoustics or tactile vibrations for decision makers to assess, and hence optimize the customer experience. Subjective assessment using Driver-in-Loop simulators to experience data has been shown to improve the quality of vehicles and reduce development time and uncertainty. Efficient development processes require a seamless interface from detailed CAE simulation to subjective evaluations suitable for high level decision makers. In the context of perceived vehicle vibration, the need for a bridge between complex CAE data and realistic subjective evaluation of tactile response is most compelling. A suite of VI-grade noise and vibration simulators have been developed to meet this challenge.