## 4 Discussion
### Limitations and Future Work  
This work has provided interesting results while also suffering some limitations. Firstly, because of the initial aim of this exploration, we did not opt for a rigorous recording strategy such as the ones we see in environmental research [35]. Further analysis and information on this soundscape would be of great interest, such as a recent study on tonal languages such as Mandarin [36]. Such a study would answer the will of customers for more \"realistic\" sounds to be brought to their vehicles. It would also review advice made in several research works [20; 37]. Secondly, we could still provide a frequency analysis of the recorded sounds. It emphasized some specific frequencies as more represented in certain types of warnings. Comparing such frequencies with the ones used inside the vehicle's ADAS allowed us to provide suitable frequency bands where alert detectability is enhanced. Here again, similar research has already been conducted, for instance, in Shenzhen and Shanghai regarding noise annoyance [38; 39]. The analysis could, therefore, be deepened and consolidated by further research in other Chinese cities as well as specified on-road environments. Thirdly, from our customer-based analysis, we experienced a positive evaluation of ADASs, although Shanghainese users showed some difficulty in understanding their system alerts. On that matter, several previous works in Europe have suggested that realistic sounds inside vehicles may help drivers better perform and retain sound information. This was not explored in our research. Still, we have found some hints that it could be the case in an environment such as the Shanghainese environment. For instance, the ADAS alert sounds were rated as neither realistic nor abstract by users. Yet these same users were hoping to have some realistic sounds provided in their future ADAS. Further research on the understanding of the notion of realistic sounds could be started, particularly in developing the understanding of ecological sound perception. Fourthly, from a marketing point of view, it would be interesting to further research and evaluate the marketing and sales impact of sounds constituting the ADAS alerts on a brand image, for example. Another research topic would be to evaluate the introduction of standardization across such auditory alerting systems, as recently reviewed by the academic world [40]. Fifthly, the final test conducted suggests that a rise in the evaluation of satisfaction, or mental and temporal demand, results in an increase in reaction time. It is difficult to draw conclusions on such observations considering the small sample used. We could still suggest that satisfaction may be linked to a \"secure\" feeling regarding the system. Feeling more secure and more confident leads to longer reaction times. Similarly, an increase in workload would decrease the capacity to react quickly. In a study by [PERSON] et al. [41] on the impact of auditory continuous feedback on Level 3 automated driving takeovers, it was found that, compared to no feedback, the number of glances toward the road increased with all three types of auditory feedback designs. However, none of the designs shortened the reaction time to imminent events. Finally, two interesting research axes concern the research on human-automation interactions. It would be of interest to evaluate the influence of the supergun's prevalence in the Shanghainese environment, both regarding alert types and information conveyance, for instance, with onboard assistants.