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Since currently a technological shift from automobiles with internal combustion engines now to electric vehicles occurs, new challenges in vehicle acoustics must be met. Although, one of the core duties of NVH engineers will still be the prevention and treatment of disturbing noises, the targeted creation of intended and designed sounds will gain in importance significantly. This sound design task is no longer a choice but a necessity. In the scope of hybrid and electric cars a new kind of acoustic feedback must be created. Surely, the simple electric motor sound, the “tram on wheels”, will not be the final solution accepted by customers. Besides the mandatory use of technical methods like transfer path analysis enabling the reliable identification of the reasons for acoustical problems by separation of sources and transfer paths or binaural panel contribution analysis, investigations of customer preferences on the basis of simulated and real test drives will become more important.

Sound quality of vehicles has become very important for car manufacturers. This feature is interpreted as among the most relevant factors regarding perceived product quality. Since the development cycles in the automotive industry are constantly reduced to meet the customers' demands and to react quickly to market needs, ensuring product sound quality is becoming increasingly difficult. Moreover, new drive and fuel concepts, tightened ecological specifications, increase of vehicle classes and increasing diversification, etc., challenge the acoustic engineers trying to create and preserve a pleasant, adequate, harmonious passenger cabin sound. Another aspect concerns the general pressure for reducing emission and fuel consumption, which lead to vehicle weight reductions through material changes also resulting in new noise and vibration conflicts.

The development of a new method to evaluate the NVH quality of diesel combustion noise bases upon following questions by regarding typical driving modes: Driving behavior with diesel vehicles Which driving situation causes an annoying diesel combustion noise Judgment of diesel combustion noise as good or bad A suitable test course was determined to regard typical driving situations as well as the European driving behavior. Vehicles of different segments were tested on that course. The recorded driving style and the simultaneously given comments on the diesel combustion noise results to a typical driving mode linked to acoustics sensation of diesel combustion noise. The next step was to simulate this driving mode on the chassis dynamometer for acoustical measurements. The recordings of several vehicles were evaluated in listening test to identify a metric. The base of metric was objective analyses evaluating diesel combustion noise in relevant driving situations.

Sound quality of vehicle is more and more an important product feature which significantly influences the perceived product quality. Over recent years, the broad variety of new models, which resulted in increased competition, has lead to rising customer demands with regard to NVH (Noise, Vibration and Harshness) aspects. Apart from the indispensable troubleshooting, the acoustic engineer's scope of work is extended to NVH design engineering. Thus, innovative, ambitious measurement technologies were developed to meet these new, challenging tasks and to maintain a competitive advantage.

Pass-by measurements on a test track are a standard test procedure for every new vehicle. Since there are only a few test tracks and the measurements are depending on the environmental conditions two indoor test procedures have been developed using a chassis dynamometer in a semi anechoic chamber. The first procedure delivers the standard pass-by analyses as well as monaural and binaural time signals using a far field array measurement. The second procedure delivers more detailed information about the different noise sources at the vehicle. Near field measurements of the main noise sources of the vehicle are combined with the airborne transfer functions between these sources and a far field observer position to get a simulated far field microphone signal of the whole vehicle or any set of components

Over the years many publications and surveys were conducted in the context of human sensation concerned with sound perception and sound quality. But an exploration of associations, feelings and context of hearing in an interactive evaluation context is needed to provide insight into the affective and cognitive parameters of sound evaluation. It has to be understood that laboratory evaluation has to be considered in the context of an artificial interruption of daily life experience. Therefore, the concept of sound quality evaluation needs to be broadened to integrate a subjective and psycho-social approach. The method AISP (Exploration of Associated Imaginations on Sound Perception) will be introduced here for benchmarking in context to appropriately evaluate the sound of the corporate identity.

Feeling and hearing the results of engineering decisions immediately via a “virtual car” - simultaneous engineering - can significantly shorten vehicle development time. Sound quality and discrete vibration at the driver's position may be predicted and “driven” before the first prototype is built. Although sound cannot yet be predicted in an unknown chassis, the sound and vibration behavior resulting from a new engine, never previously installed in a given vehicle, may be predicted, heard binaurally and felt in an interactive “drivable” simulation based on transfer path analysis. Such a simulation, which includes the binaural sound field and discrete vibration of steering wheel and seat, can also include wind and tire noise to determine if certain engine contributions in sound and vibration may be masked.

Aurally-adequate sound measurement technology makes use of both present psychoacoustic knowledge, e.g. loudness, roughness, fluctuation, sharpness and so forth, and Artificial Head measurement technology with transmission characteristics comparable to human hearing. By taking into account psychoacoustic evaluation parameters very often good results for judging sound events with regard to sound quality, as compared to subjective impressions, can be achieved. If a sound situation is relatively complex, i.e. if it consists of various single sound sources at different spatial positions, significant level and phase differences between the left and right ear occur which - in comparison with a monaural evaluation - can yield different results. Such effects have been observed for some time already. Speech intelligibility in a noisy environment, e.g., depends on the positions of the sound sources.

Measuring sounds inside cars often presents a difficult task for the acoustic engineer. Because sound events in cars arise in a complex way, direct conclusions about sound components subjectively judged to be annoying with regard to their causes and transmission paths, can be drawn in a limited way only. A new procedure, complementing binaural measurement technology and tested by including multi-channel measurements of acceleration sensor signals, sound radiation and transmission, has been developed. This involves correlating signals influencing sound quality, analyzed by means of human hearing, with signals from different acceleration sensors fixed in front of and behind engine mounts. An exact relationship between physical causes and subjectively perceived sound quality can be established.

Often the perceived annoyance of noise does not correspond with the A-weighted sound pressure level. The disagreement is because of the unique directional and pattern-recognition properties of human hearing. Therefore the importance of psychoacoustic attributes, such as perceived loudness (considering masking effects) roughness (modulation of tonal components), sharpness (relationship of high-frequency components to low-frequency ones), harmony (distribution of tonal components), spatial selectivity and so on, is becoming appreciated. The correlation of objective measurement and subjective classification of noise can be improved by considering the final receiver, “human hearing”, and developing methods of deriving and analyzing metric data based on human hearing.

The noises produced by motor vehicles and their effects on human hearing can only be described incompletely using commonly applied methods of objective measurement. Using the binaural technique based on an artifical head measurement system or an external ear simulator, subjective effects of noises can be investigated faithfully taking properties of the human ear into consideration.