Understanding and improving methods for exterior sound quality evaluation of hybrid and electric vehicles (original) (raw)
Related papers
2013
Electric vehicles are quiet at low speeds and thus potentially pose a threat to pedestrians' safety. Laws are formulating worldwide that mandate these vehicles emit sounds to alert the pedestrians of the vehicles' approach. It is necessary that these sounds promote a positive perception of the vehicle brand, and understanding their impact on soundscapes is also important. Detection time of the vehicle sounds is an important measure to assess pedestrians' safety. Emotional evaluation of these sounds influences assessment of the vehicle brand. Laboratory simulation is a new approach for evaluating exterior automotive sounds. This study describes the implementation of laboratory simulation to compare the detection time and emotional evaluation of artificial sounds for an electric vehicle. An Exterior Sound Simulator simulated audiovisual stimuli of an electric car passing a crossroad of a virtual town at 4.47 ms-1 (10 mph), from the perspective of a pedestrian standing at the crossroad. In this environment, 15 sounds were tested using experiments where participants detected the car and evaluated its sound using perceptual dimensions. Results show that these sounds vary significantly in their detection times and emotional evaluations, but crucially that traditional metrics like dB(A) do not always relate to the detection of these sounds. Detection time and emotional evaluation do not have significant correlation. Hence, sounds of a vehicle could be detected quickly, but may portray negative perceptions of the vehicle. Simulation provides a means to more fully evaluate potential electric vehicle sounds against the competing criteria.
Evaluation of sounds for hybrid and electric vehicles operating at low speed
PsycEXTRA Dataset, 2000
Electric vehicles (EV) and hybrid electric vehicles (HEVs), operated at low speeds may reduce auditory cues used by pedestrians to assess the state of nearby traffic creating a safety issue. This field study compares the auditory detectability of numerous synthetic sounds for hybrid and electric vehicles operating at a low speed. The sample includes pedestrians who are sighted and legally blind, independent travelers, with self-reported normal hearing. The test site has the acoustic characteristic of an urban area with a typical ambient noise level of approximately 58-61 dB (A). Dependent variables include proportion of detection and detection distance. Synthetic sounds tested, that resemble those of an internal combustion engine (ICE) vehicle, produce similar detection distances as the actual ICE vehicle tested for a 6 mph constant speed operation. In some instances, synthetic sounds designed according to psychoacoustic principles were detected much sooner than the reference ICE vehicle tested. Synthetic sounds that contain only the fundamental component of combustion noise, but lack the harmonics and other high-frequency characteristics of an actual ICE were relatively ineffective, with their detection distances being only about half of those of an ICE vehicle.
Electric Vehicle Sound-Expert User Perception
ASME-DETC2013, 2013
As electric vehicles are moving in on the automobile market, safety relating to acoustic perception is an important issue. It is a growing concern, particularly with respect to pedestrians, cyclists or visually impaired people. This can be addressed by adding sounds to the vehicle whilst at low speed. However, adding artificial sounds to an electric vehicle begs the question as to what kind of sound is appropriate. Appropriateness concerns technical specifications and is also linked to affective reactions of recipients of such a sound. Emotional reactions to 17 artificial exterior sounds for electric vehicles were investigated in an experimental setting with a total of 40 participants, 34 novice users and six sound experts.
Detectability and annoyance of warning sounds for electric vehicles
The Journal of the Acoustical Society of America, 2013
Electric or hybrid vehicles are very quiet at low speeds, which represents a very good opportunity to reduce traffic noise annoyance in cities. On the other hand, this may be very hazardous for vulnerable pedestrians (e.g. visually impaired people). The aim of the eVADER project is to propose solutions in order to add warning sounds to such cars, while fulfilling two contradictory goals : sounds should be detectable but should not contribute to traffic noise annoyance. Different perceptual experiments have been conducted : the first one evaluated the influence of various timbre parameters on sound detectability. It was shown that an electric vehicle equipped with one particular sound was as easily detected as a diesel one, while keeping a very low level. Then the influence of some timbre parameters (pitch and temporal modulation frequency) on the distance and speed as perceived by listeners was measured. Finally, a third experiment was devoted to the consequence on traffic noise annoyance of such warning sounds.
Wow, what car is that?: Perception of exterior vehicle sound quality
Noise Control Engineering Journal, 2003
Up until now most research and application in vehicle sound quality has been directed at describing interior vehicle sound quality. Even though the interior sound of a vehicle is a major component of the perceived sound quality, exterior sound is audible both to potential users and bystanders. It may be argued that interior vehicle sound quality is concerned with meeting the buyerʼs expectation, whereas exterior sound quality concerns a) attracting attention and positive responses of potential customers and b) minimizing negative responses in the general public. It may therefore be argued that optimizing exterior sound quality will benefit both consumers and the community. This article describes an approach to perceived exterior vehicle sound quality. To attain an understanding of exterior sound, we investigate both the semantic descriptions that are elicited when different exterior sounds are heard and specific situations (i.e. a given sound/vehicle in a given environment). Across different sounds and driving conditions we find four subjective dimensions: loudness/annoyance, perceived quality, low-frequency content, and temporal variations. This factor structure allows discriminating the sound quality of a variety of modern cars. In more specific tests we find that participants both discriminate between different vehicles and different environments (free field conditions, urban driving conditions as well as different street shapes). These results indicate that designing and predicting exterior sound quality is a multidimensional task that requires different approaches than those traditionally used for interior sound quality.
PROMET - Traffic&Transportation, 2014
The paper discusses the issue of adding artificial warning sounds to hybrid and fully electric vehicles in order to increase traffic safety by making these vehicles audible at low speeds. The goal of this modification is to enable the pedestrians to perceive possible danger coming from such a vehicle in time to respond accordingly. Following the results of previous research which state that the sounds of internal combustion engines are valid candidates for artificial warning sounds, a preliminary examination of the suitability and acceptability of different engine sounds in various modes of operation has been conducted. The chosen modes of operation are running in idle, at 2,000 rpm and 3,000 rpm with the vehicle stopped. Both gasoline and diesel engines were investigated. To expand the range of engine sounds, the type of vehicles was not limited to personal cars. The results show significant differences in suitability of engine sounds for the stated purpose, with vehicle type being the main differentiating factor.
Sound quality evaluation of electric cars : preferences and influence of the test environment
2011
Many are the upcoming noise, vibration and harshness (NVH) challenges regarding electric vehicles (EV), not least due to absence of the masking combustion engine noise. In general, sound and vibration levels in the car's interior are significantly lower for EV's. However, tonal sounds caused by electromagnetic forces in the electric motor are in varying degrees present and provide audible feedback of operation during driving. The key question for how to target these sounds is to gain an understanding about what sound quality means for EV's. As an initial study, investigations were carried out to determine how the test environment influences the evaluation of the sound perception in an EV. Headphone evaluation with playback of binaural head recordings in both listening lab and a vehicle demonstrator "sound car" were compared to the real perception in a production-like electric car. A modified established scorecard for internal combustion engine (ICE) powertrain ...
Assessment of warning sound detectability for electric vehicles by outdoor tests
2017
Electric Vehicles (EV) are characterized by a high reduction of the acoustic emission. The absence of warning sounds entails a risk situation for pedestrians. The previous research is focused on detectability of warning sounds in different noise environments. These experiments are performed indoors, where a pedestrian’s conditions are not similar to real road crossing. Drivers’ behaviour study demonstrated that different environments and workload have influence on reaction time. Consequently, this paper proposes a methodology for the analysis of detectability of real warning sound using a dynamic subject. The sample was composed by 65 participants walking around a pedestrian area. Participants had to react when they detected a vehicle approaching. The subject’s response was affected by background noise, therefore, this parameter was measured. The results establish that power levels have influence on the detectability. There is an optimum power level which improves efficiency of vehi...
A Case Study: The Urban Residents’ Choice for Electric Vehicles Warning Sounds
American Journal of Environmental Science and Engineering
Nowadays, people are exposed to noise on a daily basis. Therefore, in an overvibrant urban environments electrical vehicles operating at low speed are too quiet to be detected by pedestrians (especially vulnerable group are visually impaired people) and urban residents in general. Thus, electric vehicle warning sounds are sounds created to alert and warn pedestrians to the presence of electrical vehicles (e.g. hybrid electric vehicles, plug-in hybrid electric vehicles and all-electric vehicles) moving at low speeds. The goal of this paper is to determine through a case study what the pedestrians would desire and prefer the electrical vehicle warning audio signals to sound like. The case study involved 201 participants who had the task to fulfil a specially designed questionnaire for this purpose. Regarding the questionnaire, the participants were not prepared in any way for the testing they were just advised to keep in mind that the warning sound they select for the "role" of a pedestrian should not be irritable at the same time for the "role" of a driver. The results obtained from the questionnaire were analyzed and discussed in the paper. When speaking about the concept of smart cities and the legislation around the whole world today this is certainly a hot topic where the opinion of pedestrians and future drivers should not be overlooked.