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System and component target setting for noise and vibration are important activities within automotive product development. New challenges arise when electric motors are introduced into cars traditionally powered by combustion engines. The emitted noise from an electric traction motor for hybrid electric vehicles is characterized by high frequency tonal components from the dominating magnetic harmonics which can be perceived as annoying. Sound power is frequently used for quantifying the airborne noise from rotating electrical machines. This paper describes the process of determining the radiated sound power from an automobile electric rear axle drive in-situ and its contribution to interior cabin noise for a prominent rotor order. The sound power was calculated by combining the average stator surface vibration velocity together with an estimate of the radiation efficiency.

The increased focus and demands on the reduction of fuel consumption and CO2 requires the automotive industry to develop and introduce new and more energy efficient powertrain concepts. The extensive utilisation of downsizing concepts, such as boosting, leads to significant challenges in noise, vibration and harshness (NVH) integration. This is in conflict with the market expectation on the vehicle's acoustic refinement, which plays an increasingly important role in terms of product perception, especially in the premium or luxury segment. The introduction of the twin charger boosting system, i.e. combining super and turbo charging devices, enables downsizing/speeding in order to achieve improved fuel economy as well as short time-to-torque, while maintaining high driving dynamics. This concept requires also extensive consideration to NVH integration. The NVH challenges when integrating a roots type supercharger are very extensive.

In the vehicle development process, targets are defined to fulfill customers' expectations on acoustic comfort. The interior complete vehicle acoustic targets can be cascaded down to system and component targets, e.g. insulation properties and source strengths. The acoustic transfer functions (ATFs) from components radiating airborne noise play a central role for the interior sound pressure levels. For hybrid vehicles fitted with an electric traction motor, the contribution of high frequency tonal components radiated from the motor housing needs to be controlled. The interior sound pressure due to an airborne motor order can be estimated by surface velocities and ATFs. This study addresses the ATFs measured from a large number of positions located around an electric rear axle drive (ERAD) and their influence on estimated interior noise. First, the magnitude variation between the individual ATFs and how it clearly can be visualized was presented.

Subjects who are well aware of what to judge commonly yield more consistent results in laboratory listening tests. This awareness may be raised by explicit instructions and training. However, too explicit instructions or use of only trained subjects may direct experiment results in an undesired way. An alternative is to give fairly open instructions to untrained subjects, but give the subjects a chance to get familiar with the product and context by, for example, riding a representative car under representative driving conditions before entering the laboratory. In this study, sound quality assessments of interior sounds of cars made by two groups were compared. In one group subjects were exposed to the same driving conditions that were later assessed in a laboratory listening test by taking them on a ride in one of the cars to be assessed, just before entering the laboratory. In the other group subjects made the laboratory assessments without prior car riding.

Absorptive and isolating encapsulations or enclosures are commonly encountered around different noise-emitting components within the car industry. Not least for electric drive units, whose air borne noise shares often are dominant in the 2-6 kHz region, encapsulations can provide a cost and weight efficient noise abatement solution. The main constrains related to the acoustic performance when designing an encapsulation for electric drive units are surface coverage due to geometrical complexities, allowable package space (setting limits for maximum thickness of the encapsulation), weight and finally cost. The numerical simulation techniques for quantifying the acoustic performance in terms of insertion loss are challenging, since the encapsulations are partly compressed and far from homogeneous for example.

In the automotive industry, there is an increasing need for gaining efficiency and confidence in the prediction capability for various attributes. Often, one component or sub-system is used in a number of car models of one vehicle platform. Many of these components are potential sources of noise, vibration and squeak and rattle. In order to provide an early prognosis, vibro-acoustic source characterization in combination with the source-to-response transfer behavior are required. This paper describes the process of predicting the vibrational behavior due to a woofer, which could induce squeak and rattle, on a door panel. Blocked forces, determined indirectly in-situ by frequency response functions and operational accelerations, were used for quantifying the source activity. Those forces were in a second step loaded on to a finite element model in order to predict the response when the speaker was mounted to another position in an upcoming car model.

When it comes to the acoustic properties of electric cars, the powertrain noise differs dramatically compared to traditional vehicles with internal combustion engines. The low frequency firing orders, mechanical and combustion noise are exchanged with a more high frequency whining signature due to electromagnetic forces and gear meshing, lower in level but subject to annoyance. Previous studies have highlighted these differences and also investigated relevant perception criteria in terms of psycho-acoustic metrics. However, investigations of differences between different kinds of electric and hybrid electric cars are still rare. The purpose of this paper was to present the distribution of tonal components in today's hybrid/electric vehicles. More specifically, the number of prominent orders, their maximum levels and frequency separation were analyzed for the most critical driving conditions. The study is based upon measurements made on 13 electrified cars on the market.