© Faculty of Mechanical Engineering, Belgrade. All rights reserved FME Transactions (2017) 45, 448-458 448 Received: October 2016, Accepted: December 2016 Correspondence to: Dejan Matijević, M.Sc. Faculty of Mechanical Engineering, Kraljice Marije 16, 11120 Belgrade 35, Serbia E-mail: dejanm@viser.edu.rs doi:10.5937/fmet1703448M Dejan V. Matijević Ph.D.Student University of Belgrade Faculty of Mechanical Engineering Teaching Assistant School of Electrical and Computer Engineering of Applied Studies Belgrade Vladimir M. Popović Associate Professor University of Belgrade Faculty of Mechanical Engineering Overview of Modern Contributions in Vehicle Noise and Vibration Refinement with Special Emphasis on Diagnostics This paper presents certain considerations related to noise, vibration and harshness issues on modern motor vehicles. The first, practical aspect was used toward structuring of the acquired knowledge and relationships, required for proper problem diagnosis. On the other hand, advanced signal analyses are considered. The influence on human body is processed and certain noise and vibration analyzers are presented. This synergy of scientific and applicative approach represents a basis for further research related to this important automotive branch. Keywords: noise, vibration, harshness, diagnostics, analysis. 1. INTRODUCTION Strong market competition with high demanding customers requires appropriate vehicle systems optimization with special emphasis on vehicle noise and vibrations characteristics. Noise and vibrations of motor vehicles are increasingly important for the automotive industry, especially for vehicle manufacturers and component suppliers. The exterior noise is generally regulated by noise pollution legislation, while the interior noise and sense of vibrations are much strictly evaluated by customers themselves. Toward accomplishing extraordinary vehicle performance, there is a tendency in the vehicle design process of utilization of light weight metals in vehicle components manufacturing. Lighter weight metals decrease the overall vehicle weight that reduce emissions and improve fuel economy, but lighter vehicle components do not absorb noise and vibrations as well as heavier components, what causes many additional concerns for engineers. Noise, vibration and harshness (NVH) have become increasingly important automotive branch as a result of demands for increasing vehicle refinement. In order to achieve desired vehicle performance NVH engineers should collaborate closely with Powertrain, Electrical & HVAC, Body & Trim, Chassis & Suspension Departments as well as with Assembly Plant Engineers and Suppliers [1]. This synergic approach is indispensable in the design process of a new model. But test procedures, either for redesign purposes or during exploitation, are no less complicated. For their proper implementation multidisciplinary knowledge and skills with sophisticated sotware support are required toward identifying the root causes of faults and problems. This paper provides a short overview of some researches related to NVH refinement issues, with professional approach to diagnostic of practical problems. 2. CHARACTERISTICS OF NOISE, VIBRATION, HARSHNESS Noise is defined as any unpleasant or unexpected sound created by a vibrating object and has an increasing importance to vehicle users and environments. Vibration is defined as any objectionable repetitive motion of an object, back-and-forth or up-and-down and represents an important issue closely related to reliability and quality of the vehicle. Harshness is customer perception which creates the impression of lack of isolation from the tire/wheel and suspension system. Harshness is related to the quality and transient nature of vibration and noise, because of vehicle incapacity to absorb vibrations produced by road conditions [2, 1]. 2.1 Noise It is well known that sound is a result of mechanical vibrations which act in the elastic medium. Sound source produces a certain amount of sound energy per time, which means that the sound source is determined by sound power, which does not depend on the characteristic of the environment. On the other hand, sound intensity which is measured on a certain spot depends not only from the power of sound source and distance from it, but also from the amount of energy absorbed by the environment [3]. This explains the significance of sound insulation in qualitative assessment of cabin noise, especially to aerodynamic, road and powertrain noise. related Table 1 shows the percentage contribution of different noise sources, originating from powertrain, into total noise [4]. Table 1. Percent contribution of different noise sources into total noise Sr. No Source % Contribution I Engine 22 to 30 II Exhaust system 25 to 35 III Intake system 05 to 15 IV Fan and cooling system 07 to 15 V Transmission 12 to 15 VI Tires 09 to 15