The sounds of the Polestar 2
Electric propulsion is the way forward (pun intended). With all of the advantages electric motors bring to the table, there is simply no comparison with internal combustion engines. There's only one thing they have that electric drivetrains don't. The noise. As loud as they can sometimes be (looking at you, drivers with aftermarket mufflers), the familiar rumble of the engine was one way to know that cars were approaching.
Electric vehicles don't have this built-in noise alert system. And as much as we present the silence of EVs as an advantage (it is), we admit that it's less than optimal that pedestrians can't hear the approach of a Polestar.
Regulations have sprung up around the world in response to this situation, mandating that electric vehicles must have some sort of system that emits sounds when traveling under a speed of between 20 and 30 km/h (12-19 mph), depending on the market.
An acronym for “Acoustic Vehicle Alerting System,” AVAS is the system that gives all fully electric Polestars their sounds. And because we can design the sounds ourselves, our cars don't have to sound like a tent in a hurricane. We went with an approach of “sustainable and responsible sound design.” The sounds should be non-intrusive and non-polluting, forming a natural part of the urban soundscape. Furthermore, they should be recognizable and localizable (that is to say, it should be easy to determine where the sounds are coming from).
It should also be easy to determine what the Polestar is doing based on sound alone. To that end, the sound engineers have developed three distinct sounds for when the Polestar is driving, backing up, or idling.
The driving sound is described as a “subtle blend of noise components that resemble road noise with a sound resembling that of an electric motor.” This makes it recognizable from the outside, easily masked on the inside, and lets pedestrians know that it's a car and not the USS Enterprise that's approaching. The backing-up sound is not unlike the “backup beep” of larger vehicles, but a much more subtle and refined version. The idling sound is a modulated mix of airy sounds designed to let those around the Polestar know that it's on, even if it's stationary.
So that covers the sounds. As they're intentionally made, and not a byproduct, there's an entire process behind their creation.
First, the placement of the speaker has to be optimized. It needs to sit in that sweet spot that ensures maximum radiation of sound outwards and minimal radiation of sound inwards. Those inside the Polestar 2 don't need to be told that it's moving, after all.
Second, the team begins “sound sketching” – connecting sound design software to the speaker and testing different sounds in accordance with both brand guidelines and optimal frequency range.
Then it's time for initial tuning. Sounds are loaded into the car and mapped to car signals, such as speed. They are then adjusted and mastered until they've met the legal requirements.
A panel of listeners is recruited for the next step: testing in car. This is when the Polestar is driven under real-world conditions to measure the effectiveness of the sounds.
Finally, they move on to final verification, and the Polestar 2 is silent no more.
Sound design is being taken to new places thanks to the inherent silence of EVs. This is the Wild West of sound engineering: a previously unexplored frontier where things can be experimented with and the box can be thought outside of.
And on the horizon, a Polestar can be heard.
To read more about the various safety features and innovations found in all Polestar cars, click here.
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