Creating Sound and Providing Acoustic Ecology: THOR AVAS

Electric Vehicles (EVs) are garnering worldwide attention due to their many advantages over vehicles powered by internal combustion engines. Global EV sales have increased by roughly 30% annually over the past decade, according to data compiled by the World Economic Forum and Statista. The eco-friendliness of EVs due to zero CO2 emissions is one of the significant quotients contributing to their rise in popularity. Additionally, electric vehicles are propelled by motors that produce minimal to no noise or vibration while operating at peak efficiency. 
On the other end of the spectrum, however, the low sound emissions have led to new challenges regarding acoustic warning systems, particularly for the safety of pedestrians, cyclists, animals, and those with physical limitations. The European Blind Union (EBU) made a concerted effort to draw attention to the dangers of silent transportation, which can accelerate from zero to a hundred miles per hour in under ten seconds. This could pose a serious threat to the visually challenged. In light of the growing concerns, UN 138 legislation requires that all electric and hybrid vehicles sold in the European Union be equipped with an Acoustic Vehicle Alerting System (AVAS) in effect from July 1, 2021.

What’s the Solution?

As part of its commitment to public safety and compliance with EV legislation, we at THOR AVAS conduct our operations in accordance with the UN 138 legislation currently in effect, aiming to improve the acoustic ecology of cities with synthetic, artificial intelligent acoustic vehicle warning systems. Solutions such as THOR AVAS, THOR EV, and THOR Classic have been developed with the highest possible level of synchronization. The primary emphasis was placed on creating electric vehicle warning sounds by transforming a wide variety of noise into notes that are harmonious and audio effects that are multi-layered and sonically pleasing.

Let's take a detailed look at the various meticulously crafted layers that are a part of THOR AVAS and understand better how each of them works:

The Engine Simulation Layer

The Engine Simulation Layer comprises components of synthetic data that are generated using oscillators to recreate an engine's realistic sounds in AVAS electric cars. High frequencies are removed from the layer via filtering, leaving behind a tonally grounded base. Because of this process, the engineers at THOR AVAS are able to imbue the sounds with a particular atmosphere and synchronize them with the layers of additional notification, both of which are constructed on the tonic note. At all target frequencies, the result is a pure, dynamically rich sound unique for each package, with no unwanted sonic distortion.

The Additional Alert Layers

The additional alert layers produced by THOR AVAS are made up of melodic sequences that are either based on synthesized samples of plucked instruments or processed samples of bells and integrated into AVAS electric scooters and AVAS electric mopeds. These AVAS audio layers are included in the AVAS sound package and can be used at 10 kilometers per hour (approx. 6 mph). They continue to gain intensity and volume up to a speed of 40 kilometers per hour (approx. 24mph), where the announcement character peaks, reaching a maximum range of AVAS dynamics. The note Sol (G) of the third octave, which resonates at a frequency of approximately 1600 (1568) Hz, is used to determine the tonic. As a result of the short duration of the samples and the relatively fast "attack" of these instruments, they are plainly audible but do not sound harsh or intrusive to the human ear and do not have a significant impact on the overall AVAS dynamic.

The Vehicle Acceleration/Deceleration Layer

Additional non-musical layers that make up the vehicle acceleration/deceleration layer bring additional attention to the moment when the vehicle is accelerating. Furthermore, it provides "feedback" to the driver regarding the acceleration time. The AVAS audio data collected for this layer comes from an extensive sonic palette ranging from the foundational sounds of small motors to the movements of large industrial turbines, depending on the desired intensity level. A pedestrian may be alerted by the sound of a growing hum sampled from the mechanics of a turbine or a whistle, both of which are immediately associated with the sound of an accelerating engine. During acceleration, the layers are engineered with the package's original electric vehicle sounds using THOR AVAS' patented technology, which creates a pleasant AVAS soundtrack that is harmonious and noticeable. As the car moves, accelerates, decelerates, starts, and stops, the solution can accurately replicate the sampled audio in real-time synchronization with the movements.

Electric Vehicle Safety and the Importance of Acoustic Ecology

In response to growing concerns about the environment, governments and automakers all over the world are beginning to investigate the viability of electric vehicles as a sustainable transportation option. Everyone agrees that these have the potential to make significant improvements to air quality and dramatically cut down on noise pollution. And when we say dramatically, we mean it!

Nations worldwide have started modernizing their legal frameworks and adopting AVAS systems to reduce the number of accidents caused by the low levels of electric vehicle sounds. Most AVAS systems currently flooding the market make harsh squeaking or beeping noises for warning pedestrians. This contradicts current concepts of acoustic ecology of future cities and standards for pedestrian safety systems. In consideration of the UN 138 Regulation, the acoustic ecologies of modern towns and cities, and the diverse environments from busy city centers to peaceful residential neighborhoods, expressways, and winding country lanes, THOR AVAS came up with different solutions that are composed and crafted to create beautiful and acoustically acceptable AVAS soundtracks for EVs. 

Our system is based on software that consists of several complex components, such as a sound engine, porting library, AVAS sound profiles, and an API protocol for interacting with software. Such a dynamic sound engine is highly responsive to changes in volume, speed, vehicle characteristics, and accelerator/brake pedal placement and functions in tandem with the geolocation information transmitted by the telematics unit. The electronic connection module also has onboard memory for software and a Bluetooth interface for remote management via an app for iOS and Android devices. Both the onboard power supply and the data bus (CAN, UART, RS285, or RS482) are connected to the electronic module. Additionally, it is also possible to connect it through a telematics device or the regular power button.

The sound library is our crowning achievement which features the most extensive collection of high-quality sounds, all captured from actual vehicles using patented recording techniques. The library is constantly being expanded with new AVAS soundtracks, some of which are safety-related, while others are more for entertainment, like the instantly recognizable ice cream truck sound or the "jingle bells" tune. 

The AVAS sounds were designed to achieve AVAS's objectives by catering to the firm's specific needs. The purpose of their creation was not to add to the city's already overwhelming level of noise. In addition to being tried out in specially designed soundproof chambers, our soundscapes are also put through an AVAS test outdoors. They were found to be effective at minimum volumes and on those frequencies naturally present in the urban landscape.

With more than five years of experience developing acoustic vehicle alerting systems for electric vehicles that have been put through extensive AVAS tests in an anechoic chamber, engineers at THOR spend a great deal of time modifying and syncing sounds from a variety of noise environments, dissecting them into notes, and ultimately creating a musical AVAS soundtrack for the electric vehicles of the future. 

Article written by Charlon Muscat