eVADER: A Perceptual Approach to Finding Minimum Warning Sound Requirements for Quiet Cars (original) (raw)
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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.
On Adding Sound to Quiet Vehicles
Proceedings of the Human Factors and Ergonomics Society, 2008
Alternative energy vehicles such as hybrids and electric tend to run quieter than many hydrocarbon fueled vehicles. Their relative quietness could negatively affect pedestrian and driver safety because of reduced sound cues compared to louder vehicles. The present study examined preferences for sounds that might provide an acceptable auditory cue to quiet vehicles. Participants heard and then rated 18 sounds (3 variations in six categories). Each sound was displayed in conjunction with a video of a moving hybrid vehicle. The sounds of an engine, white noise, and hum sound in that order were most preferred as added sound to a quiet vehicle. 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.
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.
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.
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.
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...
Auditory Perception of Motor Vehicle Travel Paths
Human Factors: The Journal of the Human Factors and Ergonomics Society, 2012
Objective-These experiments address concerns that motor vehicles in electric engine mode are so quiet that they pose a risk to pedestrians, especially those with visual impairments.
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.