Hidden treasures: the secrets of the Renault's anechoic chambers

Every morning, Stephane drives along Normandy country roads, where only his car and a few morning birds break the silence of nature as it wakes from its evening slumber. The calm soon gives way to the hubbub of the Aubevoye Technical Centre, Renault's testing and engineering facility located 100 km northwest of Paris. Behind the vast main gates, the site extends over more than 600 hectares of land cut off from the public and includes nearly 60 km of test tracks, 44 test lines, two wind tunnels, 18 corrosion chambers, and much more. The testing facilities serve to put future Renault Group vehicles through their paces in wide range of situations, all secretly hidden away in the Eure forests.

Stephane passes a series of check points and security gates under the watchful gaze of security guards, as he enters centre. Engineers, technicians, pilots, experts of all kinds: roughly 1,000 specialists work at the state-of-the-art site. Walking through the maze of corridors, Stephane shows us around his workplace. It is made quickly apparent that it looks nothing like your regular office...

Sound barriers

The walls and ceiling of the first room are covered with foam panels of horizontal and vertical prisms. The protruding forms dissipate sound waves instead of reflecting them, removing any echo from the room, hence the name ‘anechoic’. "As the floor is not covered, we should say ‘semi-anechoic’ chamber," says Stéphane.

Here, the word ‘silence’ takes on new meaning. One truly hears nothing; the absence of sound becomes stifling. In such a space, void of all other background noise, the second you move, the slightest sound of a crumpling fabric or even a breath becomes surprisingly perceptible. Conversely, the sound of a clapping hand seems muffled, dull even, because the walls don’t produce an echo. Stephane smiles, "It is such a unique experience!"

The Renault ZOE, a pioneer of electric vehicles ten years ago, raised a number of completely new issues pertaining to sound. What to do with all the silence? Renault used the anechoic chambers to develop a VSP (Vehicle Sound for Pedestrians) so that pedestrians could hear ZOE cars approaching at low speeds. "A car that plays the Traviata or Wagner would be fun, but it opens up a Pandora’s box of noise pollution issues," jokes Stéphane. The All-new Megane E-TECH Electric will still emit a selection of sounds to warn pedestrians.  

Inside, with the purr of the combustion motor no longer present, the soundscape now requires particular attention to detail: "We are now focusing more on the noise made by turn signals, the clicking sound of buttons, beeps played by touch-screen interfaces. Drivers and passengers are at the heart of an acoustic and sensory experience that is all part of the driving experience.”

Hitting the right wavelength

Not far away, another special room piques one’s interest. This is where Xavier works as Electromagnetic Compatibility Expert. The walls are covered with white panels, that sit atop a thick layer of insulation. Another All-new Megane E-TECH Electric is being tested on a chassis dynamometer to simulate driving on the open road. All around antennae bombard the car with electromagnetic waves of varying intensities and frequencies. Vehicles in the real world are constantly subjected to electromagnetic fields, be it when passing by phone towers, television transmitters, or automatic speed radars, so all precautions must be taken to ensure that nothing interferes with the normal running of the vehicle.

We are in a Faraday cage. The walls of this room block electromagnetic waves and isolate us from the outside world. We can therefore test how the car transmits and receives all sorts of waves: radio, telephone, or GPS.

While there are fewer sound waves around vehicles, the same cannot be said for electromagnetic waves. Since the beginning of the century, the number of on-board electronic devices has increased fourfold. The Renault Megane E-TECH Electric boasts new connected functions and ADAS. This added connectivity means that there are more waves bouncing around both inside and outside the car. It is therefore essential to ensure that frequencies do not interfere with each other to avoid any on-board equipment malfunctions or safety issues outside the vehicle, thereby ensuring safe and reliable vehicles for all Renault customers.

The day of the visit, Renault’s new flagship car and all its equipment was being put through numerous tests – twice that required by regulation. Every response and behaviour is closely checked live from the control room. Everything is dissected and analysed with the help of powerful computers. There is no room for doubt when it comes to guaranteeing performance and reliability of the car's connected systems.

From test chambers to the road