On – Road Evaluations.
We’ve had the opportunity to observe how a group of NVH experts from an OEM evaluate the sound to a premium sports car on the road. Our analysis revealed that assessors employ two strategies to evaluate the sound of the car. They have a predetermined methodology, which considers, the type of road and specific driving manoeuvres. Using this methodical approach, they evaluate the sound in two ways. Top down and bottom up. For the former, they evaluate the sound as a whole, for the latter they mentally decompose the sound and evaluate each of many different acoustic features and identify their sources. Their driving behaviour serves to excite the sources to enable them to hear them more clearly. The assessor also demonstrated the use of schemas as reference for the car they were evaluating. It was evident that they placed the cars in a perceptual space defined by other vehicle with stereotypical acoustic characters, and also believed they were judging the car from the customers’ perspective. We published this work at the SAE NVH 2009 conference and at Internoise 2009.
Influence of company identity:
Does company identity influence the evaluation of automotive sounds belonging to cars of a similar performance level, and from the same market segment? This question has important implications for industry because target setting within automotive companies involves comparing the sound of cars that the company manufacture with the sound of competitor cars. Participants listened to target sounds, belonging to two different manufacturers, along with control sounds. Before hearing each target sound participants saw either the correct company identity for the sound they were about to hear, the incorrect company identity, or were given no information about the manufacturer of the car. Company identity did not influence how target sounds were evaluated; displaying company identity did not interfere with participants’ appraisals of high performance cars belonging to different manufacturers. This work is awaiting publication.
Perceptual dimensions for Electric Vehicle Sound Quality:
NVH engineers make use of 2 dimensional spaces to quantify Sound Quality characters for existing and concept vehicles. One dimension often relates to the perception of performance, the other to perception of refinement and luxuriousness. However, as pure Electric Vehicles (EVs) may now find mainstream uses, it was necessary to evaluate whether the same perceptual dimensions could be used for these vehicles, which have different powertrain architectures. This was accomplished by exploring the language used by people to describe their reactions to, and their expectations of, the sound of an EV. Lexicon was captured from several sources, including online forums, structured evaluations and the media’s portrayal of EVs. The lexicon was first characterised using content analysis, and then reduced using Principal Component Analysis. Using this approach, 3 perceptual dimensions have been identified. Two of the dimensions are synonymous to the traditional Sound Quality perceptual dimensions; these are “powerfulness” and “refinement”. The third dimension is related to how “futuristic” the vehicle sounds. This work was published at Internoise 2010. Our next step is to understand where different sounds can be placed within the three dimensional space.
Our findings also provide an overview of the new challenges that will need to be addressed to ensure the exterior sound of an EV caters the safety of pedestrians and contributes towards the creation of a positive soundscape, this is an area that we are beginning to address through our use of ELVIN.
We are planning to conduct a study aimed at understanding how people’s expectations of a vehicle influences their driver behaviour. This study will conducted in the driving simulator.