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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.

Realistically experiencing the sound and vibration data through actually listening to and feeling the data in a full-vehicle NVH simulator remarkably aids the understanding of the NVH phenomena and speeds up the decision-making process. In the case of idle vibration, the sound and vibration of the idle condition are perceived simultaneously, and both need to be accurately reproduced simultaneously in a simulated environment in order to be properly evaluated and understood. In this work, a case is examined in which a perceived idle quality of a vehicle is addressed. In this case, two very similar vehicles, with the same powertrain but somewhat different body structures, are compared. One has a lower subjective idle quality rating than the other, despite the vehicles being so similar.

The sound of the engine has a significant influence on the driver's perception of the performance, comfort and quality of a vehicle and hence their overall satisfaction with the product. Therefore achieving the right engine sound inside the vehicle is one of the key deliverables in the NVH process. In the case of a vehicle fitted with an internal combustion engine this is usually done by tuning the mechanical components whereas in quiet vehicles (e.g. Hybrid or Electric) a virtual engine sound can be generated using sound synthesis algorithms incorporated into the vehicle's electronic systems. In either case, the task of developing an appropriate engine sound can be made more robust, efficient and understandable by using an NVH Simulator, which is an interactive tool for auralising and evaluating all NVH data (Test and/or CAE) in the correct context (i.e. while driving) at all stages in the development of a vehicle.

A new approach to achieve better customer perception of overall vehicle quietness is the sound balance improvement of vehicle interior sound during driving. Interior sound is classified into 3 primary sound source shares such as engine sound relative to revolution speed, tire road noise and wind noise relative to vehicle speed. Each interior sound shares are classified using the synchronous time-domain averaging method. The sound related to revolution order of engine and auxiliaries is considered as engine sound share, tire road noise and wind noise shares are extracted by multiple coherent output power analysis. Sound balance analysis focuses on improving the relative difference in interior sound share level between the 3 primary sound sources. Virtual sound simulator which is able to represent various driving conditions and able to adjust imaginary sound share is built for several vehicles in same compact segment.

This work presents an application of airborne source path contribution analysis with emphasis on prediction of wideband sounds inside a cabin from measurements made around a stand-alone engine. The heart of the method is a time domain source path receiver technique wherein the engine surface is modeled as a number of source points. Nearfield microphone measurements and transfer functions are used to quantify the source strengths at these points. This acoustic engine model is then used in combination with source-to-receiver transfer functions to calculate sound levels at other positions, such as at the driver's ear position. When combining all the data, the in-cabin engine sound can be synthesized even before the engine is physically installed into the vehicle. The method has been validated using a powertrain structure artificially excited by several shakers playing band-limited noise so as to produce a complicated vibration pattern on the surface.

Source-Path-Contribution (also known as transfer path analysis or noise path analysis) comprise a well-known set of techniques that have traditionally been performed in the frequency domain. With advancements and modern techniques, these same principles can be applied accurately in the time-domain. Foremost among the benefits of this are an ability to analyze transient events, and the ability to listen to the contributions from various sources instead of merely viewing them. This paper demonstrates the analysis of a diesel engine vehicle utilizing time-domain source-path-contribution techniques.

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.

In a traditional NVH development process, the realization of the targeted vehicle acceleration sound quality can be a highly laborious and costly process involving the creation and evaluation of multiple iterations of prototype parts. Consequently, development engineers are limited by long prototype part fabrication times while key product decision makers have to often accept the “in-process” sound quality due to aggressive program timing milestones and escalating program costs. The NVH simulator provides an alternative approach that is potentially more efficient in terms of reducing program timing, reducing development and prototype costs and improving the end-product sound quality. This paper presents the case of a V6 vehicle under development whose acceleration sound quality needed improvement. The NVH simulator was used to determine the key contributors that lead to the sound quality of the targeted vehicle.

Shock absorber transient noise, often referred to as “chuckle” or “loose lumber”, has been a vehicle level noise and vibration concern for many years. The noise often occurs with lightly damped shock tuning under small road inputs at low speed. This transient type noise is of particular concern to the operator because it can sound like mechanical looseness in the chassis. This noise concern is generally addressed late in the design cycle and the options of a fix are limited to a change in damper tuning or added mass. A need for a wider design envelope exists to address this concern which must include noise paths into the structure and body sensitivity. The study documented in this paper walks through the process of acquiring this noise on the road and reproducing it in the lab on a 4-post hydraulic test rig.

In this paper a time-domain version of source-path-contribution analysis is investigated using a controllable source, an engine noise and vibration simulator installed into a trimmed vehicle, and compared to the results obtained using a more traditional frequency-domain source-path-contribution analysis. Both airborne and structure-borne inputs are investigated and the matrix method is used to calculate source contributions as sounds at a listeners' position inside the cabin. Operating data from a simulated run-up/run-down and sets of transfer functions (FRFs) are firstly used to estimate the strength of some defined point sources, acoustically and mechanically. Secondly the operating source strengths are combined with acoustic or vibro-acoustic FRFs to predict contributions at a receiver. In this work it is attempted to make the airborne and structure-borne models as simple as possible, and predicted contributions are validated against actual measured data.

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.