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The science of silence

If you thought electric cars were quiet, think again. DS Automobiles is on a mission to make sure Nº8 is the last word in refinement. It starts at the very beginning

Partnership content, funded by DS AUTOMOBILES Bauer Media Registered Company Number LP003328 (England and Wales) Registered Office: The Lantern, 75 Hampstead Road, London, NW1 2PL

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Words: Piers Ward I Photography: Lee Brimble

It’s only when one of your five senses disappears that you’re aware of how important they all are. It’s a feeling highlighted when the vast, soundproofed door at DS Automobiles’ research and development facility closes behind us. Moving on well-greased hinges, it glides to a close with a solid thunk. It’s as if the air in the room stops moving. Something feels off - you know your ears are working but all you can hear are echoes in your brain. This is the semi-anechoic room at the Stellantis group’s Belchamp site (‘semi’ because the floor isn’t sound-proofed). It’s been used by DS to perfect the noise, vibration and harshness (NVH) levels on the new Nº8. For DS, the ambition is to get close to silence, and to cocoon the occupants in elegant comfort. The level of detail is staggering, to the point where DS doesn’t want the Nº8’s occupants to be able to hear any noise the car itself generates, such as the Acoustic Vehicle Alerting System that’s designed to warn pedestrians about oncoming vehicles. So the prototypes we see and drive have no artificial engine sound. As Eric Senes, director of NVH in West Europe for Stellantis, puts it: ‘We want to be quiet. DS is very strong on silence.’ Being electric, the Nº8 has presented new challenges to the engineers. All cars suffer from airborne and structural noise, but EVs are more susceptible to a third type, road noise. Senes explains: ‘People thought acoustics engineers could rest because of battery electric vehicles, but that was wrong. Other noises have emerged across low, medium and high frequencies.’

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Every element of the car has been investigated to find where noise can be eliminated. That includes moving parts, like the powertrain internals and suspension, but also those areas where different components meet - for instance the gorgeously shaped body and the structural reinforcement beams inside; you don’t think of them as producing any noise, but when you’re as focused as DS engineers then you leave no stone unturned. Senes says his team added insulation to various components, and asked the engineers to close some of the holes in the body to reduce wind noise to an absolute minimum. The NVH team got involved right at the start, while the car was still being designed, to help shape the A-pillars and wing mirrors around which so much wind noise is generated. Particular attention was paid to the seals where the mirrors join the body, and to the triple-seal door system (two seals on the door itself, one on the body). As he is showing me around the car, Senes points at the bonnet strut. Surely that can’t be important? But no, even this most humble of components has been given the DS treatment, with insulating padding fitted around it to cushion any vibrations. Senes is also very demanding with suppliers, setting higher standards because it’s an EV, which means any creaking will be more noticeable. And he’s equally demanding with his production-line colleagues, specifying with great precision the gaps in the bodywork, to eliminate wind noise where possible. Big gaps allow more noise, he explains, as do inconsistent gaps.

Old challenges like fitting doors snugly and new challenges like muffling the whine of an electric motor are all part of the job for Eric Senes and his noise-reduction experts

Cutaway is a rare chance to understand just how complex a car seat is, with so many potential sources of noise

He proudly highlights the rear seats. ‘Not a lot of people pay attention to this area. But rear door handles can be close to ears, so it’s important to make sure the shapes and seals around them work well.’ If you’re wondering why there’s an air outlet in the DS Nº8’s rear wheelarches, you can thank Eric Senes. The role of the vents is to gently eliminate any build-up of air in the rear of the car, which could cause vibrations to reverberate through the boot. The focus on silence has involved DS refining every element of the Nº8 during its creation. Even the seats have been studied and researched with noise and vibration is mind. While we are at Belchamp, we get the chance to inspect a cutaway front seat - a rare opportunity to appreciate the staggering complexity of this often-overlooked part. It’s vented in both the back and the squab, and heated, and uses high-density foam to spread weight more evenly. Sitting in one, we find it to be comfortable, with good support both under the thigh and at your sides - but not too much; it doesn’t feel like it’s pinching your chest in, more a reassuring hug of leather and foam. DS set a target that the temperature could be -5ºC outside and you’d be able to sit in the car in just a shirt because the Nº8 can heat itself so quickly. Key to this is the neck warmer, a vent in the seat that distributes air forward. We’ve used the word ‘distribute’ deliberately because it doesn’t blow the air - DS wanted the experience to feel less like standing in a wind tunnel and more like air is being gently diffused around the cabin.

Interestingly, DS has not employed any active noise cancelling, choosing instead to perfect the acoustic experience in a passive manner. The reasoning is that it’s difficult to eliminate road noise entirely because there are so many frequencies at play and it’s better to cover those by insulation rather than any speaker-operated system. It’s difficult to argue with that strategy when the end result is so convincing. In an early prototype drive near the Belchamp centre in eastern France, it’s staggering how well resolved and calm the Nº8 feels. DS provides two key rivals for comparison, and the difference is remarkable. Where they judder down the road, the Nº8 merely shimmies; when you’re in the Nº8 you’re aware the tarmac isn’t perfect, but it’s not an annoyance. It’s a remarkable achievement for a prototype driven well in advance of production commencing, and speaks volumes to the efforts of all the DS engineers.

All this additional technology on the car presents Senes with more headaches, because every part adds to the noise he’s on a mission to minimise - ‘if it rotates, it makes noise,’ as he says. For instance, his team worked closely with the thermal cockpit team to prioritise NVH during those times when air is flowing from the vents only gently; the aim is to make sure the reduction in noise from the airflow does not reveal mechanical sound from the vents. Similarly, the motors in the massage seats came in for close scrutiny. All this has been rigorously modelled and then tested, in the lab and on the road. Stellantis takes research and development very seriously, so its facilities have the ability to test for all sorts of conditions, with a climate chamber that can replicate winds of 230km/h (143mph), temperatures from -30ºC to 50ºC, humidity from zero to 100 per cent and a sunlight intensity equivalent to Death Valley. DS talks of the ‘close comfort’ test, designed to make sure features such as the seat heating and neck warmer get up to temperature quickly enough. The engineers even leave a bowl of water in the car to check the demist function works correctly.

Noises most of us wouldn’t even notice are eliminated through rigorous work during the development process

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