The Effect of a “Design-of-Awareness” Process on Recognition of AVAS Sound of Quiet Vehicles

Abstract

The development of quiet vehicles, such as hybrid and electric vehicles, has environmental benefits. However, the quietness of these vehicles may increase the risk to pedestrians, particularly those with visual impairment. We hypothesized that a “design-of-awareness” process based on the concept of sound education for hearing and recognizing the sound generated by the Acoustic Vehicle Alerting System (AVAS) installed in quiet vehicles may change peoples’ attitudes toward the sound and improve their ability to detect it. To verify this hypothesis, two experiments using a quiet vehicle were conducted to examine whether participants were able to detect the AVAS sound. The results revealed that few participants were initially able to detect the AVAS sound. After the design-of-awareness process was conducted, 1 and 3 month follow-up surveys were conducted to clarify its effects and longevity. The results revealed that approximately half of the participants became able to detect the sound, and that their attitudes toward the sound were changed. In addition, the number of participants who were able to detect the sound increased over time. These results indicate that a design-of-awareness process could be helpful for training people to detect the sound of quiet vehicles.

1. Introduction

Quiet vehicles such as electric and hybrid vehicles (EV/HVs) are becoming increasingly widespread internationally because of their low carbon dioxide emissions and other environmental benefits [1,2]. These vehicles emit less noise than internal combustion engine (ICE) vehicles, particularly at low speeds, contributing to a reduction in environmental noise. Misfariis et al. [3] reported that noise levels were clearly different at vehicle speeds under 10 km/h, with the electric vehicles being more than 10 dBA quieter than ICE vehicles. These quiet vehicles may pose an increased risk to pedestrians if they are too quiet to detect under noisy urban conditions. When the background noise level in an environment in which quiet vehicles are running at low speed is less than 55 dBA, a vehicle with an engine is clearly audible, whereas an electric vehicle is not [3]. Sekine et al. [4] reported that most of the 40 participants in their study (15 of whom were visually impaired or otherwise disabled) did not detect the approach of quiet vehicles driving below 10 km/h. To address this issue, the first guidelines for quiet vehicles were published in Japan in 2011 [5]. These guidelines were translated and modified, and finally published as international guidelines in 2016 (UN Regulation No. 138 on Quiet Road Transport Vehicles) [6]. These guidelines mandated the installation of an additional sound-emitting system intended to enhance pedestrians’ awareness of quiet vehicles. This sound-emitting system was named the “Acoustic Vehicle Alerting System (AVAS)”, which creates a sound to inform pedestrians of the car’s approach within a speed range of 0–20 km/h. These regulations included requirements regarding the acoustic characteristics of AVAS sounds, such as the minimum sound level, frequency spectrum, and frequency shift of the sounds. To improve awareness of the AVAS sounds of quiet vehicles, various studies have been conducted internationally [3,7,8]. Pilskow et al. [9] conducted a sound detection experiment regarding the AVAS sounds of quiet vehicles with blind and visually impaired participants. The results revealed that a hybrid electric vehicle was detected by blind participants at a shorter distance and with less time to avoid a collision compared with traditional ICE vehicles traveling at slow speeds. In addition, Roan et al. [10] reported that EV/HVs were detected at significantly shorter distances by visually impaired participants relative to ICE vehicles when traveling at 10 km/h. Moreover, although mean detection distances tended to be higher for quiet vehicles with an AVAS sound, it was not significantly different from the detection distances for traditional EVs at speeds of 10 km/h. These results indicate that an easier-to-detect AVAS sound needs to be developed. However, there are many issues that need to be addressed, such as the balance between understandability and maintaining non-noisy characteristics, and the requirement that the sound not be masked by background noise. Regarding the driver’s perspective, Cocron [11] reported that noise-related concerns among EV drivers diminished with increasing driving experience. These findings suggest that improving pedestrians’ awareness of quiet vehicles is important to avoid accidents. On the basis of these reports, the development of approaches for improving people’s recognition and attitudes toward the AVAS sound of quiet vehicles may be helpful for improving awareness of these vehicles. Schulte-Fortkamp [12] suggested an approach for addressing this issue on the basis of the soundscape proposed by Schafer [13]. Schafer also proposed a sound education program that was based on the concept of a soundscape [14]. In this sound education program, some activities such as soundwalking (walking through any environment without talking, focusing our listening on every sound around us) were proposed for training people in “hearing techniques”, with opportunities being provided to listen to sounds that exist in the environment in their daily lives [14]. The positive effects of sound education have been widely reported, particularly in the field of education [15,16]. On the basis of the sound education concept and these previous findings, we hypothesized that providing people with the opportunity to recognize and hear the AVAS sounds of quiet vehicles could change people’s attitudes toward the sounds and improve their ability to recognize them. We named this process “design-of-awareness”. To verify this hypothesis and clarify the effects of the design-of-awareness process regarding the AVAS sound of quiet vehicles, we conducted two experiments. To investigate the issues regarding the quietness of EV/HEVs, the experiments were conducted in a quiet area at low speed so that the vehicle’s ICE would not engage and thereby generate engine sound. In addition, we investigated the sounds that people actually heard and used to recognize the approach of quiet vehicles in daily life, including the AVAS sound.

2. Experiment 1: Effect of the Design-of-Awareness Process

To examine the effects of the proposed design-of-awareness process, we conducted an experiment in which people were provided with the opportunity to hear and recognize the AVAS sound of a quiet vehicle. In addition, we performed a follow-up survey.

2.1. Experimental Conditions

The experiment was conducted at the comprehensive traffic test road at Nihon University on 12 October 2016. The University is situated in a quiet residential area. The test road was 30 m wide and 618 m long, and it consisted of dense-grained asphalt concrete over the entire length. In the experiment, an AVAS-equipped 2015-model hybrid car (Prius, Toyota Motor Corporation, Aichi, Japan) was used as the quiet vehicle. The positions of quiet vehicles and participants are shown in Figure 1. The quiet vehicles drove from AA’ to BB’ at a constant speed (15 km/h). This speed was selected because the AVAS sound is emitted at speeds below 20 km/h, as well as to ensure participants’ safety. The speed was measured using a speed gun. Participants stood 2 m from the center line of passing quiet vehicles near the PP’ line in Figure 1. The sound pressure level of background noise (L_Aeq: equivalent continuous A-weighted sound pressure level) was measured several times before the experiment using a sound level meter. Each measurement was conducted for 10 s, during which other specific noises were not detected. The average background noise level was 41.4 dBA. The experimental conditions are shown in Figure 2.

The participants were 12 students at Nihon University (11 males and one female) with an average age of 21.5 years. To investigate the effect of the design-of-awareness process, the participants should ideally be unfamiliar with the AVAS sound. Therefore, sighted young students were recruited as participants, rather than visually impaired people. Although five participants reported in a survey conducted after the experiment that they were already aware of the existence of the AVAS sound, none of them had actually heard it before the experiment, and this was confirmed in the experiment.

2.2. Materials and Methods

To prevent participants from intentionally directing their awareness to the AVAS sound, the experimenters provided a false description of the purpose of the experiment, stating “In this experiment, we want to confirm the difference between the traveling speed of vehicles and the perceived speed”. Participants were required to verbally report the perceived traveling speed of vehicles after the quiet vehicle drove by in front of them. The conditions of the experiment and the participants’ responses were recorded using a video camera.

The following protocol was conducted as the design-of-awareness process. After all participants reported the perceived traveling speed of vehicles, the experimenter explained the AVAS sound. Subsequently, participants verbally reported whether they noticed the AVAS sound or not. This interview was conducted simultaneously with all participants because of the need to standardize the timing for questioning the participants as to whether they were aware of the AVAS sound. In addition, the interview needed to be completed in a short time so as not to overburden the participants. After the interview, the quiet vehicle again drove by at a speed below 20 km/h until all participants correctly recognized which sound was the AVAS sound of the quiet vehicle.

2.3. Results

Before participating in the design-of-awareness process, all participants reported that they did not notice the AVAS sound, even though five of them were already aware of the existence of the AVAS sound before participating in the experiment. For example, participants reported “I did not notice the approaching vehicle by the sound” and “I thought that (the AVAS sound) was a necessary sound produced by the vehicle running, such as the sound of the motor”. As expected, it appeared to be difficult for participants to recognize the quiet vehicle’s AVAS sound when they did not have sufficient experience hearing and recognizing the sound.

2.4. Follow-Up Survey

After the interview and participating in the design-of-awareness process, participants’ email addresses were collected with their consent. One month after the experiment, on 11 November 2016, the experimenter sent participants a link to a questionnaire survey created using Google Forms (Google, Menlo Park, CA, USA). Participants were asked to answer the questionnaire survey online. The question items in the survey are shown in

Table 1. Question items used in the follow-up survey.

Question No.	Question Items
1	Did you notice the AVAS sound of quiet vehicles in daily life after participating in the experiment?
1-1	(if answered “Yes” in Q. 1) How many times did you notice the AVAS sound?
1-2	(if answered “Yes” in Q. 1) What was the road condition when you noticed the AVAS sound?
1-3	(if answered “Yes” in Q. 1) Where did you notice the AVAS sound?
2	Did your attitude toward the AVAS sound change after participating in the experiment?
3	Did you talk about the AVAS sound to someone?
3-1	(if answered “Yes” in Q. 3) Who did you talk to about the AVAS sound?

. Answers were obtained from nine of 12 participants. Examples of the answers are shown in

Table 2. Participants’ answers to the question items used in the follow-up survey.

Participants	Q. 1	Q. 1-1	Q. 1-2	Q. 2	Q. 3	Q. 3-1
A	No	–	–	Not much	No	–
B	Yes	3 or 4	Mix of residential and shopping area	Slightly yes	No	–
C	Yes	More than 10	Residential area, downtown area, and mix of residential and shopping area	Neither	No	–
D	Yes	1 or 2	Mix of residential and shopping area	Neither	No	–
E	Yes	3 or 4	Residential area	Neither	No	–
F	No	–	–	Slightly yes	Yes	Family and friends
G	No	–	–	Not much	No	–
H	No	–	–	No	Yes	Friends
I	No	–	–	Yes	Yes	Friends

for each question item. Each participant is designated by a letter, and the shaded cells indicate whether or not they were aware of the existence of the AVAS sound before participating in the experiment. It should be noted that living environments differed from participant to participant; therefore, the opportunities and conditions under which the participants encountered the quiet vehicles or heard the AVAS sound after the experiment might have differed between the participants.

Although the experiment was conducted under quiet conditions, four participants (B, C, D, and E) reported that, after the experiment, they were able to notice the AVAS sound in daily life under noisy conditions. Of these four participants, only B reported that they became able to consciously hear the AVAS sound after participating in the experiment. The other three participants (C, D, and E) did not recognize a change in their attention to the AVAS sound. This may have been because they were already aware of the AVAS sound before participating in the experiment and may have, therefore, already have been more attentive to it than the other participants. In contrast, participants F and I reported that they became able or slightly able to consciously hear the AVAS sound, although they did not notice the sound in daily life. Furthermore, three participants (including F and I) talked about the AVAS sound to their family or friends after participating in the experiment.

These results revealed no clear relationship between the change in attentiveness toward the AVAS sound and awareness of that sound in daily life. However, some participants became able to notice the AVAS sound after they had the opportunity to hear the sound in the experiment. In addition, some participants who were not able to detect the AVAS sound immediately after the experiment recognized a change in their attitudes toward the sound and reported that they later became able to consciously hear the AVAS sound.

3. Experiment 2: Long-Term Effect of the Design-of-Awareness Process

The results of Experiment 1 indicated that participants did not notice the AVAS sound emitted from the quiet vehicle, regardless of whether they were already aware of the AVAS sound. An effect of the design-of-awareness process on participants’ concern toward the sound was observed. The persistence of the effect of the design-of-awareness process was not examined in Experiment 1. However, we hypothesized that if the effect of the design-of-awareness process was long-lasting, the relationship between noticing the AVAS sound and a recognizable change in attitudes toward the sound would be more clearly observed when a longer period of time has passed after the experiment. To test this hypothesis, the design-of-awareness process was conducted in a second experiment (using the method described in Experiment 1) and follow-up surveys were conducted 1 and 3 months after the experiment. The experiment was conducted without visual information to investigate the sounds that participants actually heard, and to examine which sounds were used to detect the approach of quiet vehicles.

3.1. Experimental Conditions

The experimental conditions were the same as those used in Experiment 1. The experiment was conducted on 16 October 2018. The participants stood 2 m from the center line of the quiet vehicle near the PP′ line in Figure 2 (Section 2.1), forming a line with 1 m intervals. The experimental scene is shown in Figure 3. During the experiment, participants paid attention to the sound emitted from the quiet vehicle while standing with their back to the car and their eyes closed. The quiet vehicle passed behind the participants three times. The participants were students attending Nihon University. Of the participants, 11 were male and one was female, with an average age of 21.7 years. None of the participants had taken part in Experiment 1. Seven participants were aware of the existence of the AVAS sound before participating in the experiment. The experiment was recorded using a video camera.

3.2. Materials and Methods

As in Experiment 1, to avoid the participants intentionally directing their consciousness to the AVAS sound, the experimenters provided a false explanation, stating “This experiment aims to measure the distance at which pedestrians sense danger in relation to the approaching vehicle”. Participants were required to raise their hand when they felt danger regarding the approaching vehicle. The experiment was conducted twice with the car emitting the AVAS sound. The experimenter conducted interviews in which participants were asked about what sounds they used to detect the approach of the quiet vehicle and what sounds caused them to sense danger. Subsequently, participants verbally reported whether they noticed the AVAS sound or not. The experimenter then explained the AVAS sound. This interview was conducted simultaneously with all participants, as in Experiment 1. Following the methods in Experiment 1, we also conducted the design-of-awareness process, and participants were exposed to the AVAS sound repeatedly until they were able to recognize it. The same experiment was then conducted again.

3.3. Results before Conducting the Design-of-Awareness Process

The experimental results obtained from the interview before conducting the design-of-awareness process are shown in

Table 3. Interview results after the experiment before the design-of-awareness process was conducted.

Participants	What Factors Did You Use to Detect the Approach of the Vehicle and to Recognize Danger?	Did You Notice the AVAS Sound?	(If You Noticed the Sound) What Did You Feel about the AVAS Sound?
A	Sound of the motor and road noise	Yes	It needs to be louder to be noticed
B	Sound pressure of sound	Yes	The sound did not effectively indicate danger
C	Sounds that were unique to the Prius	No	–
D	Road noise and the sound of the motor	Yes	It was hard to notice
E	Driving noise that gradually increased	No	–
F	Driving noise that gradually increased	No	–
G	Approaching sound of car and wind noise	No	–
H	Driving noise that gradually increased Low frequency sounds become audible	No	–
I	Engine sound and sound emitted from tires	No	–
J	Increase in sound pressure level of driving noise	Yes	The sound can be heard in a quiet area, but it might become hard to hear in a noisy area
K	Driving noise that gradually increased	No	–
L	Driving noise that gradually increased	No	–

. Each participant is indicated by a letter. The shaded cells indicate whether or not each participant was aware of the AVAS sound before participating in the experiment. As shown in Table 3, only one-third of participants were able to detect the sound, and all of these participants were aware of the existence of the AVAS sound before participating in the experiment. However, none of the participants reported that they noticed the approach of the quiet vehicle and recognized danger using the AVAS sound. Participants who did not notice the AVAS sound reported that “I did not recognize the sound as a notification sound” and “I noticed sounds other than the AVAS sound, such as road noise and the noise of the vehicle running”. As in Experiment 1, it appeared to be difficult for participants to notice the AVAS sound if they did not correctly recognize the sound.

Other sounds, such as the sound of the motor, road noise, and wind noise, were frequently used as clues to detect the approach of the quiet vehicle. It should be noted that one participant answered “engine sound”, although the quiet vehicle did not drive using an ICE during the experiment. These reported sounds are emitted not only from quiet vehicles but also from ICE vehicles. Therefore, the participants might use these familiar sounds to detect the approach of a quiet vehicle, rather than the unfamiliar AVAS sound. This tendency was also observed for participants who were able to detect the AVAS sound. The results suggested that participants may have never heard the AVAS sound before the experiment and could not correctly recognize it, even if they were already aware of the existence of the sound. To examine this issue, the same experiment was conducted after the design-of-awareness process was conducted.

3.4. Results after the Design-of-Awareness Process Was Conducted

The sounds used by participants to recognize the approach of the quiet vehicle after participating in the design-of-awareness process are shown in

Table 4. Sounds that the participants used to detect the approach of the quiet vehicle after the design-of-awareness process.

Participants	What Sounds Did You Use to Detect the Approach of the Vehicle and Recognize Danger?
A	AVAS sound and road noise
B	AVAS sound and road noise
C	Sound of tires rubbing
D	Road noise
E	Sounds other than the AVAS sound
F	Sound of tires slipping
G	AVAS sound or sound of tires
H	AVAS sound and sound of tires
I	AVAS sound
J	Sound of tires
K	Sound of tires rubbing
L	Sounds other than the AVAS sound

. As in Table 3, each participant is indicated with a letter, and the shaded cells indicate whether or not they were aware of the existence of the AVAS sound before participating in the experiment. Approximately half of the participants (A, B, G, H, and I) reported that they continued to use the AVAS sound to detect the approach of the quiet vehicle and to recognize danger. Participants A and B were already aware of the AVAS sound before the experiment. The other three participants (G, H, and I) were not aware of the existence of the AVAS sound before participating in the experiment. These results suggest that the design-of-awareness process could potentially contribute to more widespread use of the AVAS sound to recognize that a vehicle is approaching, regardless of whether people were already aware of the sound. Other than participants A, B, G, H, and I, despite having participated in the design-of-awareness process, the remaining participants did not continue to use the AVAS sound. These participants reported that “The AVAS sound did not sufficiently alert me to the approach of the vehicle to enable me to detect it and recognize danger”. To address this issue, further research on the design-of-awareness process and the development of design methods to improve the effectiveness of AVAS sounds for alerting pedestrians to danger may be required.

Before participation in the design-of-awareness process, ambiguous sounds such as “driving noise” tended to be reported as the factors used for recognizing the approach of the quiet vehicle and sensing danger, as shown in Table 3. In contrast, specific sounds such as “AVAS sound” and “sound of tires” were reported as factors after participation in the design-of-awareness process, as shown in Table 4. This result may have occurred because the design-of-awareness process directed participants’ attention to the sounds emitted from the vehicle, including the AVAS sound.

3.5. Follow-Up Survey

In Experiment 1, a follow-up survey was only conducted 1 month after the experiment. To confirm the effects of the design-of-awareness process and examine its persistence, follow-up surveys were conducted 1 and 3 months after Experiment 2.

3.5.1. Materials and Methods

As in Experiment 1, the questionnaire survey was conducted using Google Forms. Email addresses were collected with participants’ consent after the experiment. The experimenters sent a link to a Google Form survey via email and asked participants to answer the questionnaire survey online. The same question items in Experiment 1 (see Section 2.4, Table 1) were used in this survey.

3.5.2. Results of the Survey 1 Month after the Experiment

The results of the questionnaire survey conducted 1 month after the experiment are shown in

Table 5. Results of the follow-up survey conducted 1 month after the experiment.

Participants	Q. 1	Q. 1-1	Q. 1-2	Q. 2	Q. 3	Q. 3-1
A	Yes	More than 10 times	Residential area, and mix of residential and shopping area	Neither	No	–
B	Yes	5 or 6 times	Residential area	Slightly yes	Yes	Friends
C	Yes	1 or 2 times	Residential area	Yes	No	–
D	Yes	1 or 2 times	Residential area	Neither	No	–
E	No	–	–	Slightly yes	Yes	Friends
F	No	–	–	Not so much	No	–
G	No	–	–	Slightly yes	No	–
H	No	–	–	Slightly yes	Yes	Friends
I	No	–	–	Not so much	No	–
J	No	–	–	Slightly yes	No	–
K	Yes	1 or 2 times	Residential area	Not so much	No	–
L	Yes	5 or 6 times	Mix of residential and shopping area	Slightly yes	No	–

. Each participant is indicated by a letter, and shaded cells indicate whether or not they were aware of the AVAS sound before participating in the experiment. As with Experiment 1, the opportunities and conditions under which the participants encountered the quiet vehicles or heard the AVAS sound after the experiment might have differed across the participants because their living environments differed. As shown in Table 5, six participants (A, B, C, D, K, and L) noticed and heard the AVAS sound in daily life, under noisy conditions. Participants C, K, and L did not notice the sound when they participated in the experiment (see Table 3, Section 3.3). In addition, half of the participants (B, C, and L) reported that their attitude toward the AVAS sound had changed, and they began to consciously listen to the sound. The other four participants (E, G, H, and J) who did not notice the AVAS sound in daily life also reported that they recognized a change in their attitudes toward the sound. Furthermore, three participants (B, E, and H) talked about the AVAS sound to their friends after participating in the experiment. These results confirmed the potential of the design-of-awareness process, as well as the results of Experiment 1.

When more time had passed after participating in the experiment, participants might have been able to notice the AVAS sound in daily life because their attitude toward the sound had changed. Therefore, we next examined changes in participants’ ability to notice the AVAS sound 3 months after the experiment.

3.5.3. Results of the Follow-Up Survey Conducted 3 Months after the Experiment

The results of the survey conducted 3 months after the experiment are shown in

Table 6. Results of the follow-up survey conducted 3 months after the experiment.

Participants	Q. 1	Q. 1-1	Q. 1-2	Q. 2	Q. 3	Q. 3-1
A	Yes	More than 10 times	Residential area, and mix of residential and shopping area	Slightly yes	No	–
B	Yes	1 or 2 times	Residential area	Yes	Yes	Friends
C	Yes	5 or 6 times	Residential area	Yes	No	–
D	No	–	–	Yes	No	–
E	Yes	1 or 2 times	Residential area	Neither	No	–
F	No	–	–	Not much	No	–
G	No	–	–	Neither	No
H	Yes	1 or 2 times	Residential area	Not much	Yes	Friends
I	No	–	–	Slightly yes	No	–
J	Yes	5 or 6 times	Residential area	Slightly yes	No	–
K	Yes	5 or 6 times	Residential area	Not much	No	–
L	Yes	3 or 4 times	Mix of residential and shopping area	Slightly yes	No	–

. Each participant was designated with a letter, and the shaded cells indicate whether each participant was aware of the AVAS sound before participating in the experiment, as in Table 5 in Section 3.5.2. The number of participants who noticed the AVAS sound was increased from six to eight compared with the survey taken 1 month after the experiment. Of these, three participants (E, H, and J) had not noticed the sound 1 month after the experiment. Conversely, participant D did not notice the AVAS sound 3 months after the experiment, although they had noticed the sound 1 month after the experiment. The number of times that participants noticed the AVAS sound also increased from that 1 month after for two participants (C and K). This might be because more time passed since the survey conducted 1 month after the experiment, and the participants, therefore, had more opportunities to encounter quiet vehicles and hear the AVAS sound. As shown in Table 6, more than half of the participants reported that their attitude toward consciously hearing the AVAS sound changed. The answer “slightly yes” was most frequently chosen in the survey conducted 1 month after the experiment. However, in the 3 month follow-up survey, the number of participants choosing the answer “yes” was also increased. This suggests that some participants clearly noticed a change in their attitudes toward the AVAS sound over time. Thus, the effects of the design-of-awareness process appeared to be long-lasting and became more apparent over time.

4. Discussion

In Experiment 1, when the quiet vehicle drove in front of the participants while emitting the AVAS sound, none of the participants noticed the sound, even though five participants were aware of the existence of the sound before participating in the experiment. As expected, it was difficult for participants to notice the AVAS sound without having a sufficient opportunity to hear and recognize the sound. In Experiment 2, none of the participants used the AVAS sound to detect the approach of the quiet vehicle when they were required to use only audio information with no visual information. Participants tended to use more familiar sounds, such as the sound of the tires and road noise other than the AVAS sound. In the interview conducted after Experiment 2, four participants answered that they noticed the AVAS sound of the quiet vehicle. However, they did not sense the danger associated with the sound and, thus, did not use the sound to recognize the approach of the quiet vehicle. These results suggest the need for further development of the sound design of the AVAS sound to more clearly alert pedestrians to approaching quiet vehicles and the associated danger.

The follow-up survey conducted 1 month after Experiments 1 and 2 revealed that some participants noticed the AVAS sound in daily life. This tendency was observed regardless of the change in attitudes toward the AVAS sound. The other participants, who did not notice the AVAS sound in daily life after the experiment, also reported that they recognized a change in their attitudes toward the sound. These changes appeared to result from the design-of-awareness process. The follow-up survey conducted 3 months after Experiment 2 revealed that the number of participants who noticed the AVAS sound in daily life increased compared with the results after 1 month. This might be because as time passed, the participants had more opportunities to encounter quiet vehicles and hear the AVAS sound. The effect of the design-of-awareness process appeared to continue over a long duration and became more apparent with time.

These results indicate that the design-of-awareness process based on the concept of sound education [14] has the potential to change people’s attitudes toward the AVAS sound of quiet vehicles and improve the awareness of the sound in daily life, confirming our hypothesis. This approach may contribute to improving peoples’ awareness of quiet vehicles. In addition, some participants talked about the AVAS sound to their friends or family after the experiment, regardless of whether they noticed the sound in daily life. Thus, the design-of-awareness process may also be helpful for improving others’ recognition of the AVAS sound of quiet vehicles.

5. Conclusions

As we hypothesized, the design-of-awareness process based on the concept of sound education proposed by Schafer has the potential to change people’s attitudes toward the AVAS sound of quiet vehicles and improve their ability to detect the sound. In order to take advantage of these results, it would be needed to work not only with researchers, but also with car manufacturers and governments to make an opportunity to conduct the design of awareness process for the general public, including the visually impaired.

In the current study, the experiments were conducted on a test road consisting of dense-grained asphalt concrete located in a quiet residential area. In addition, the quiet vehicle ran at a low speed under the experimental condition. The issues related to quiet vehicles could also occur not only in quiet areas but also in urban areas. In future work, the same experiment should be conducted on other road surfaces and under other experimental conditions, such as simulating the traffic noise with loudspeaker, to reveal their effects on the design-of-awareness process. All participants in this study were young people with normal vision. The number of male participants was larger than that of female participants in both experiments. The AVAS sound of quiet vehicles is particularly important for enabling visually impaired people to detect the approach of quiet vehicles. Most previous studies of quiet vehicles with visually impaired people focused on the detectability of quiet vehicles and the effects of the AVAS sound. Future studies will be required to confirm the effects of the design-of-awareness process in visually impaired individuals.