Cars of the future will not necessarily be silent

Autonomous cars = The sound of silence? Not quite…

Volvo XC40.

Electric autonomous cars are coming, and they will be missing two things that we have come to expect from cars: noise and drivers. Right? Not quite.

While the drivers will be noticeable by their absence, the noise will not be completely gone. Mikael Ljung Aust, senior technical leader for collision avoidance functions at the Volvo Cars Safety Centre, has revealed that – for safety reasons – autonomous cars will not be completely silent.

Ljung Aust is one of Volvo Cars’ most prominent safety researchers and specialises in applying behavioural science research into crash avoidance. In the past 20 years, he has published or co-published more than 30 scientific papers on subjects such as driver distraction, collision warning and avoidance systems, as well as the potential safety impact of self-driving technology.

In order for electric autonomous cars to be safe, they will need to communicate clearly with fellow road users and Ljung Aust said sound will play an essential role – because it is easily understood by most people. “A key ingredient in designing communication is to be able to reach everyone, and sound is very good for that,” he pointed out.

So, exactly what sounds will cars of the future make? Forget about any “vroom vroom”. Slowing down and speeding up will involve a ticking sound. “You will need to show that the car is intending to slow down well before the car actually has to slow down to stop in a particular place. So, slowing down sounds very intuitive. If you have a rhythm that slows down, that goes tickticktick, tick, tick, tick… tick… tick… tick… people universally interpret this as slowing down and vice versa. If you are accelerating, if you play that sequence backwards and you go tick… tick… tick… tick, tick, tick, tickticktick, then you have acceleration,” explained Ljung Aust.

Some sounds will hardly be heard. “If you are deep into your pod on whatever you are listening to, then maybe you are going to be stepping out in front of the car anyway, even though you did not mean to. In that particular case, we are designing a warning sound that targets that pedestrian with a sound beam. With the technology we are planning to use, it is going to be inaudible to everyone but the pedestrian. You use something called ultrasonics and you play them at different frequencies, and when they hit each other and when they hit the person, they modulate down into a hearable frequency range. It is really cool tech,” he enthused.

But possibly the coolest sound that an autonomous car will make has been coined the “breathing whale” – and it will be welcomed by a pedestrian who wants to cross at a pedestrian crossing (but is not sure that the car will actually stop). It is formulated around a low-frequency sound and a slow pulse. “It oscillates very, very slowly, which indicates that you are standing still. The car just stands there, breathing very slowly, and you feel it is safe to cross,” explained Ljung Aust.

There you have it: from ticking to slow breathing… The cars of the future will not quite be silent. 

Be sure to watch this video. 

Photo: MotorPress