The Gear Whine Noise and vibro-acoustic emission of gear-box Niola V., Quaremba G. Department of Mechanical and Energetics University of Naples “Federico II” Via Claudio 21, 80125, Napoli, ITALY vincenzo.niola@unina.it http://niola.dime.unina.it/ Abstract – This article reports the results of several tests, carried out in optical gear whine noise to evaluate the difference between the vibro-acoustic emission of two gearboxes of the same type, one, in particular, showing a micro-geometrical error located on the side of tooth and characterized by lack of material at the base of the tooth due to a slight drift of the production process. The tests were carried out in fourth gear. The user of the vehicle, in fact, seems to be particularly attentive to the vibro-acoustic emissions. For that reason the major car manufacturers devote significant resources to the Noise, Vibration and Harshness sector, which deals with noise and vibration of the vehicle to the vehicle driving comfort. Key-Words: - vibro-acoustic emission, gearbox, gear whine noise, signal processing, automotive, driving comfort. 1 Introduction Continuing advances in the automotive industry in recent years, leading manufacturers of automobiles to develop more and more advanced products from technical and quality point of view. In addition, consumer needs, now aligned with the high standards achieved, prevent manufacturers to make vehicles of poor quality. This is the reason the major car manufacturers devote significant resources to the Noise, Vibration and Harshness (NVH) which deals with noise and car vibration also the driving comfort. This present work was aimed to analyze two gearboxes, made by the same manufacturer, for the objective assessment of its vibro-acoustic emissions due to the phenomenon of gear whine. 2 The problem of gear whine noise The Gear Whine Noise (GWN), as well as the gear rattle noise, is one of the main vibro- acoustic phenomena of gearbox [1,2,3]. The GWN is an acoustic problem, which can be quite fastidious in the car, because of the presence of values of frequency and sound pressure relatively high. Usually, the acoustic noise occurs at meshing frequency ranging between 50 and 90 dB (A). Because the acoustic pressure, due to GWN, is not necessarily proportional to the engine speed the unexpected noise and therefore the undesirable acoustic phenomena due to the power system could be high in any engine running condition [4]. For that reason GWN represents an important problem to solve or to reduce or to "manage" at least in an appropriate way [5]. Many factors influence the vibro-acoustic emissions; mainly they are: – Transmission error – Variation of meshing stiffness – Dynamical forces of meshing – Friction forces – Detention of air and lubricant between the teeth. 3 Gearbox: technical specifications The gearbox used for assessing the vibro- acoustic test is designed for medium-powered car and allows the transmission of a maximum torque of 350 Nm. The model has three axles and 6 speed. Recent Researches in Multimedia Systems, Signal Processing, Robotics, Control and Manufacturing Technology ISBN: 978-960-474-283-7 138