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The current figure of Diesel market share in Europe of about 50% indicates a high market penetration of the HSDI Diesel engine. Due to increasing fuel prices and limited crude oil resources the worldwide demand for Diesel engines for the passenger car sector is increasing - even in typical gasoline markets like the united States. The key factors for the further success of the HSDI Diesel engine are the fulfillment of future worldwide emission legislation and that the production costs of the technologies necessary to do so, do not make it uncompetitive in comparison to the various gasoline engine concepts. Heavy SUVs with relatively small engines will therefore have to face the biggest challenge.

Vehicle manufacturers throughout the world are facing increasingly stringent noise legislation which demands highly refined vehicles and powertrains for compliance. Further to the demanding legislative requirements, an increase in customer awareness regarding high ride comfort has forced additional refinement as regards competitive sound level and sound quality. In the commercial vehicle market this trend in increased customer awareness is growing ever more apparent, although the expectations regarding noise are, for some applications, justifiably lower than in the passenger car market. Further to legislative compliance and a competitive noise level in dB(A), noise quality issues are increasingly being addressed to satisfy customer demand. In the passenger car market customer awareness regarding noise has increased to such an extent that in order to satisfy customer expectations engineering desirable sound has become an integral requirement.

The effective identification and control of powertrain structure borne harmonic noise is a key to achieve a desired noise quality profile in a vehicle. Much work is being done in this field to refine and develop sound engineering techniques suitable for application at each stage of a vehicle development programme. For prototype development and trouble shooting, transfer path analysis and source identification techniques are in use today with varying degrees of success and application complexity. Investigation tools which are fast, do not require extensive vehicle dismantling and yet provide reliable answers, will be of value to the NVH and sound quality engineer. A new Active Path Tracking method is described which is relatively quick and offers practical confirmation of the influence of identified paths. The method involves the novel adaptation of Active Noise Cancellation techniques to the task of source identification.

The exterior and interior noise level of passenger cars has been reduced in the past to a large extent by legislation and on the demand of the car purchasers. One important marketing aspect today is the possibility to enjoy driving, which is determined by the noise quality and not the noise level inside passenger cars. However the interior noise quality of today's passenger cars does not always satisfy the people affected. In the development process of a vehicle, the noise quality is determined on a subjective basis by test drivers. A great deal of experience and time is required for the subjective assessment and for the further definition of strategies and their application to meet sound engineering targets for noise quality. This paper reports on the result of a R&D program to develop a software based Noise Quality Map with which the interior noise quality of passenger cars can be determined on an objective basis by measurement in real-time.