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The Sound Of Silence

A vehicle with an internal combustion engine produces noise – to be precise, the engine produces noise.  This is because when it’s working, the engine is continually producing controlled explosions that are used to power the vehicle. We’re all familiar with the different roars, growls and rumbles coming from different engines, with some enthusiasts being able to tell vehicles apart simply by their sounds – and some mechanics making their initial diagnoses on what the engine sounds like when it’s running. Quite a few of us have something of a fondness for different engine notes, especially those that produce low grumbling noises.

However, it’s a different story when it comes to EVs (here, we’re talking about battery electric vehicles or BEVs and hybrids when they’re running on their electric motor). Electricity makes no sound, so when an electric motor is running, there is very little noise produced. This could be though of as one of the advantages of an EV – and if you’ve tried to get some sleep when the local boy racers seem to be having a drag race on your street at 2:00 a.m., you’d probably agree. However, it can also be a disadvantage.

Pedestrians and cyclists rely on their sense of hearing a lot more than you think. Sound is often the first cue you get that a vehicle is approaching, and the sound also tells you whether it’s speeding up or slowing down, which way the vehicle is travelling and even how big it is. The art of using our ears to help us know when something’s coming is drummed into us ever since our first road safety lessons and the motto of Stop, Look and Listen.

Unfortunately, all this goes out of the window with EVs. When they’re going slowly (i.e., at below 18 km/h), they don’t make much sound at all and they’re practically silent, especially in, say, a busy supermarket carpark. At higher speeds, they aren’t so silent, as the sound of the tyres on the road (road noise) and the hiss and rush of air moving across the outside becomes a factor. Unfortunately, it’s in these low-speed environments that EVs and people are likely to come into conflict. And it can be quite dangerous.

I know this by experience. I remember a few years back, I was coming out of a supermarket and was preparing to cross the bit where the cars move (you can’t really call it a road, but you know the bit I mean). I’d looked right and seen the road was clear, then looked left and seen that there were a few cars coming along. I looked right again and saw nothing coming on that side but saw a couple of cars as they went past and away from me.  I didn’t hear anything coming from that side, so my brain told me that all the cars I had been waiting for had gone past, so I prepared to push my trolley forward.  Peripheral vision kicked in just in time to stop me walking in front of an older model EV approaching silently.

I know it had to be an older model EV, as it wasn’t until 2010 that legislative bodies in Japan, Europe and the US listened to the concerns of the visually impaired and blind community and insisted that all new EVs had to have some sort of audible warning when travelling at low speeds (including in reverse).

I think most of us who lived through the era of audible reverse warnings are grateful that the manufacturers of EVs didn’t rely on beeps or something as annoying as a neighbour I once had in his car. His played a very tinny computer-blip version of Für Elise when reversing, and this irritating tune was practically my alarm clock when my neighbour reversed out of his driveway as he headed off early to work. Elon Musk typically suggested that Tesla models should be able to produce amusing sounds as a warning, such as bleating goats, fart noises or coconut shell clippety-clop sounds. The Powers That Be in Europe, however, cracked down on that suggestion and stipulated that these low-speed warning sounds had to sound something like an actual engine. This sounds like the Powers That Be lack a sense of humour, but there is some sense to what they’re saying. For one thing, we’ve all learned the sound of an approaching car engine, so it makes sense to have the warning sound telling us that it’s a car that’s coming and not, say, a goat. If every single EV had a different sound, we’d have to somehow learn to recognize and subconsciously identify those sounds as “car coming to my left; potential threat”. It’s also been suggested by an article in The New Yorker that the growl of an engine is reminiscent of the growl of a predator, possibly triggering something primal inside us. I’m also pretty sure that farting Teslas would be funny for about five minutes, but the joke would wear off pretty quickly and just become annoying.

The designers of EVs then discovered a whole new world: the art of making an engine-like warning sound that would do its job of letting cyclists and pedestrians know a car is coming without being annoying and, well, sounding right. We respond emotionally to sounds, so designers want to come up with something that is right for their brand and image. They’ve often teamed up with composers to do this, the most notable being BMW teaming up with movie composer Hans Zimmer (composer of the music for Gladiator, some of the Pirates of the Caribbean franchise and Man of Steel). It’s quite a process and is as much of an art as a science. Should the sound replicate the noise of an internal combustion engine perfectly, or should it sound high-tech like something out of a sci-fi movie? What frequencies and harmonics can be heard by everybody? What’s not going to send the driver nuts? How can they avoid making cities noisier than they have to be?

Here are three of the ideas that designers have come up with. Which one do you like the best?

Porsche Taycan Turbo S


Audi E-tron

Jaguar I-Pace