Assessment of warning sound detectability for electric vehicles by outdoor tests (original) (raw)
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Applied Acoustics, 2014
Electrical vehicles operating at low speed are often too quiet to be detected by pedestrians in time. In order to study the efficiency of additional auditory warning signals they might be equipped with, a sample of 100 sighted and 53 blind listeners was exposed to a virtual roadcrossing scenario in which they had to detect whether an approaching vehicle came from the right or left. Nine warning signals, designed to differ in particular sound features such as FM, AM or the number of harmonics were studied and compared with the recording of an unfitted electrical vehicle (EV) and a conventional diesel car. The responses measured in the scenario in which cars approached at irregular intervals over two 20-min periods showed no reaction-time differences between blind and sighted participants, and a significant advantage when listening under dry weather conditions as opposed to recordings mixed with the sound of rain. Most importantly, however, regardless of listening conditions and the population studied (sighted or blind), the additional warning signals differed greatly in efficiency. Some signals facilitated detection of the EV as much as making it as noticeable as a control diesel car of significantly higher sound pressure level. Other signals were largely ineffective compared with the unfitted EV. Analysis of the signal characteristics suggested a relatively low number of harmonics, absence of frequency modulation, and irregular amplitude modulation to be the most salient features facilitating timely detection.
The Journal of Rehabilitation Research and Development, 2012
A repeated-measures design with block randomization was used for the study, in which 14 adults with visual impairments attempted to detect three different vehicles: a hybrid electric vehicle (HEV) with an artificially generated sound (Vehicle Sound for Pedestrians [VSP]), an HEV without the VSP, and a comparable internal combustion engine (ICE) vehicle. The VSP vehicle (mean +/− standard deviation [SD] = 38.3 +/− 14.8 m) was detected at a significantly farther distance than the HEV (mean +/− SD = 27.5 +/− 11.5 m), t = 4.823, p < 0.001, but no significant difference existed between the VSP and ICE vehicles (mean +/− SD = 34.5 +/− 14.3 m), t = 1.787, p = 0.10. Despite the overall sound level difference between the two test sites (parking lot = 48.7 dBA, roadway = 55.1 dBA), no significant difference in detection distance between the test sites was observed, F(1, 13) = 0.025, p = 0.88. No significant interaction was found between the vehicle type and test site, F(1.31, 16.98) = 0.272, p = 0.67. The findings of the study may help us understand how adding an artificially generated sound to an HEV could affect some of the orientation and mobility tasks performed by blind pedestrians.
British Journal of Visual Impairment, 2012
This study examined the effect of adding an artificially generated alert sound to a quiet vehicle on its detectability and localizability with 15 visually impaired adults. When starting from a stationary position, the hybrid electric vehicle with an alert sound was significantly more quickly and reliably detected than either the identical vehicle without such added sound or the comparable internal combustion engine vehicle. However, no significant difference was found between the vehicles in respect to how accurately the participants could discriminate the path of a given vehicle (straight vs. right turn). These results suggest that adding an artificial sound to a hybrid electric vehicle may help reduce delay in street crossing initiation by a blind pedestrian, but the benefit of such alert sound may not be obvious in determining whether the vehicle in his near parallel lane proceeds straight through the intersection or turns right in front of him.
On the Risk of Quiet Vehicles to Pedestrians and Drivers
Proceedings of the Human Factors and Ergonomics Society, 2001
Technology has enabled the mass production of hybrid and electric vehicles. Interest in these alternative-energy vehicles has been heightened due to air quality concerns in urban areas. However, these vehicles are capable of very quiet operation, which could have negative side effects on pedestrian and driver safety because of the lack of sound cues. A survey of 380 people was conducted to explore interest and concerns about electrically powered vehicles. The data show that there is substantial positive interest in driving quiet hybrid and electric cars. However, in the role of pedestrian, participants expressed concern over the reduced auditory cues to the presence of a moving vehicle. Implications of quiet vehicles are discussed including the additional consideration of reduced driver awareness of their speed. Precautionary measures and suggestions for effective engine noise substitutes are presented.
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.
eVADER: A Perceptual Approach to Finding Minimum Warning Sound Requirements for Quiet Cars
2013
The eVADER project endeavors to enhance the technology of lectric-vehicles for the safety of pedestrians, especially the visually-impaired. The research presented here focused on eVADER's goal to isolate features of replacement sounds for electric-vehicles, maximizing pedestrian safety while minimizing noise pollution. It was predicted that 3 sound features (complexity, amplitude-modulation, frequency-modulation) could be the most informative to listeners, allowing for quieter emission. Sounds were synthesized using different combinations of the 3 (features) X 3 (levels). The 9 synthesized sounds were normalized (dBA), Doppler-shifted, and superimposed onto a binaural-recording of a moving electric-vehicle (prototype-sounds). Stimuli were embedded in a noisy background (traffic or traffic + rain), emulating a suburban soundscape. In this simulation, participants were virtual pedestrians, waiting to cross a street, using only sound. In a fractional, repeated measures design, 111 ...
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.
On the hazard of quiet vehicles to pedestrians and drivers
Applied Ergonomics, 2014
The need to produce more efficient and less polluting vehicles has encouraged mass production of alternative energy vehicles, such as hybrid and electric cars. Many of these vehicles are capable of very quiet operation. While reducing noise pollution is desirable, quieter vehicles could negatively affect pedestrian safety because of reduced sound cues compared to louder internal combustion engines. Three studies were performed to investigate people's concern about this issue. In Study 1, a questionnaire completed by 378 people showed substantial positive interest in quiet hybrid and electric cars. However, they also indicated concern about the reduced auditory cues of quiet vehicles. In Study 2, 316 participants rated 14 sounds that could be potentially added to quiet alternative-energy vehicles. The data showed that participants did not want annoying sounds, but preferred adding "engine" and "hum" sounds relative to other types of sounds. In Study 3, 24 persons heard and rated 18 actual sounds within 6 categories that were added to a video of a hybrid vehicle driving by. The sounds most preferred were "engine" followed by "white noise" and "hum". Implications for adding sounds to facilitate pedestrians' detection of moving vehicles and for aiding drivers' awareness of speed are discussed.
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.