Acoustic vehicle alerting system (AVAS) audio signal analysis and processing

In recent years, there has been a notable surge in the popularity of electric and hybrid vehicles globally. As vehicle manufacturers strive to push the boundaries, their next objective is to extend the utilization of electric and hybrid commercial vehicles, encompassing buses, minibuses, trucks, tractors, and construction machinery. This advancement is poised to reduce the noise levels associated with urban traffic profoundly. However, the quiet nature of electric and hybrid vehicles, mainly when operating at lower speeds in urban environments, presents a safety concern as pedestrians and other living beings may struggle to detect these vehicles. To mitigate this risk, implementing an Acoustic Vehicle Alert System is imperative. The primary purpose of this system is to safeguard against accidents and injuries by alerting pedestrians and other living beings through specially designed synthetic sounds that align with psychoacoustic principles emitted by vehicles traveling at lower speeds. Numerous countries and regions require installing an Acoustic Vehicle Alerting System for new electric and hybrid vehicles. While this system is externally added to older vehicles to comply with regulations, it is seamlessly integrated into newly manufactured vehicles. The primary purpose of the Acoustic Vehicle Alerting System is to significantly improve the safety of electric and hybrid vehicles by issuing audible alerts to pedestrians and other individuals on the road, particularly in circumstances where the quiet nature of these vehicles may present potential hazards. In 2016, the United Nations Economic Commission for Europe (UNECE) released the UNECE-R138 regulation, while the National Highway Traffic Safety Administration (NHTSA) published the FMVSS141 regulation in the same year. These regulations establish the Acoustic Vehicle Alerting System parameters in Europe and America, respectively. They outline the necessary sound levels, frequency ranges, and methods for measuring sound in the Acoustic Vehicle Alerting System. This thesis's primary focus centers on examining and creating an Acoustic Vehicle Alerting System that adheres to the UNECE-R138 regulation in Europe. This research, which is supported by a Tübitak Teydeb project, encompasses the analysis and development of the essential sound levels, frequency ranges, and sound modulation required for the Acoustic Vehicle Alerting System. Furthermore, detailed information is provided regarding the design of electronic hardware and software that complies with the UNECE-R10 EMC compatibility regulation and the environmental conditions specified by ISO-16750 and ISO-20653 standards. The overarching objective of this project is to produce a locally designed and manufactured Acoustic Vehicle Alerting System product that offers various sound options and is adaptable to different types of vehicles, utilizing an ASIL-B functional safety level processor unit. The system's hardware, software, sound design, and validation tests were conducted, and subsequent successful results were thoroughly examined and presented. The global rise in electric and hybrid vehicles has resulted in quieter urban areas at lower speeds, which presents a significant safety concern for pedestrians and other road users. So, vehicles traveling below 20 km/h require an artificial noise that mimics the sound of traditional internal combustion engine vehicles. Consequently, there is a worldwide demand for implementing the Acoustic Vehicle Alerting System in electric and hybrid vehicles. In 2010, a Japanese automotive company introduced the first Acoustic Vehicle Alerting System, which emits audible warnings to pedestrians about the presence of approaching electric and hybrid vehicles. Recognizing the life-threatening risk to visually impaired individuals caused by the reduced sound levels of these vehicles, the American Council of the Blind advocated for regulatory measures in the same year. The Acoustic Vehicle Alerting System comprises various components, including speakers, horns, and other devices that produce sound. Depending on the system, it can be automatically activated when the vehicle is in motion or manually activated by the driver. It can also be integrated into the vehicle's existing sound system or added as an aftermarket accessory. This study focuses on developing and implementing an Acoustic Vehicle Alerting System that adheres to UNECE-R138 and UNECE-R10 automotive regulations and ISO-16750 and ISO-20653 standards. The design of the system prioritizes durability and resistance to dust. Furthermore, this universal Acoustic Vehicle Alerting System can be installed on any commercial vehicle, promoting pedestrian and overall safety during their journeys. Acoustic vehicle warning systems for electric vehicles do not have a designated Customs Tariff Statistics Position number. However, the most suitable tariff for importing and exporting such systems in Turkey falls under Chapter 85, specifically identified as 8512.30.90.00.19. This chapter encompasses "Electrical Machinery and Equipment and Parts Thereof; Sound Recorders and Reproducers; Television Image and Sound Recorders and Reproducers and Parts and Accessories of Such Articles." The tariff outlines the classification as "Electrical sound signaling equipment for cycles or motor vehicles: other: other. In order to carry out comprehensive patent research on a global scale, it is imperative to determine the appropriate International Patent Classification (IPC) code that accurately encompasses the project's scope. The relevant classification for this research is the IPC code B60Q5/008, which pertains to acoustic signal devices that are automatically activated to alert individuals to the presence of silent vehicles. Upon analyzing international patent applications, it becomes evident that there has been a substantial surge in the number of patent filings after the introduction of the Acoustic Vehicle Alerting System by a Japanese automotive company in 2010, as well as the advocacy efforts of the American Council of the Blind to implement regulatory measures. The initial step in this process involved examining the sound attributes of conventional vehicles equipped with internal combustion engines to ensure compliance with the UNECE-R138 regulation. Once these sound characteristics were analyzed, the next phase entailed developing synthetic sounds that adhered to the regulation. Sound recordings of the 95-horsepower gasoline Fiat 1.4 Fire and the 108-horsepower diesel Renault 1.5 dCi were obtained during idle periods to determine the sound characteristics of the engines. These recordings were then subjected to analysis using the Sigview signal analysis software. The findings revealed that the diesel engine emitted higher sound levels than the gasoline engine. Furthermore, the synthetic Acoustic Vehicle Alerting System sounds utilized in commercial products, such as the Nissan Leaf's Acoustic Vehicle Alerting System sound, were examined to identify the specific frequency components necessary for compliance with regulatory standards. Various techniques were explored to create artificial sounds to ensure compliance with the UNECE-R138 regulation. The Supercollider software was a valuable tool in generating synthetic engine sounds, which were then fine-tuned to align with the required frequency bands and sound levels. Additional testing was carried out using the Teensy 3.2 development board equipped with an ARM Cortex M4 microcontroller to simulate these synthetic engine sounds in a microcontroller environment. However, due to the absence of ASIL safety standards on the Teensy platform, the final design opted for the STM microcontroller and Class-D amplifier, both of which satisfy the stringent safety standards of the automotive industry. The Acoustic Vehicle Alerting System was subjected to various tests to validate its compliance with the UNECE-R138 regulation, including tests for sound pressure levels, frequency ranges, and environmental conditions. The results confirmed that the system met the regulatory requirements, and the final design was successfully implemented and tested. This summary captures the presented thesis's essence and critical findings, providing a comprehensive overview of the research and its significance in enhancing pedestrian safety by developing an effective Acoustic Vehicle Alerting System. Keywords: Acoustic Warning System, Pedestrian Safety, Electric Vehicles, Hybrid Vehicles, Synthetic Sound Reproduction