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

Renault Group has numerous testing and engineering facilities in France and around the world. One of them, located in Aubevoye, is home to a hidden treasure: anechoic chambers. Cut off from all sound waves or electromagnetic interference, prototypes of upcoming vehicles are put through extensive testing in these mysterious rooms. It is also inside these chambers where top secret testing is carried out on the sounds and connected features that are to be used on future models. Stephane, Head of Acoustics and Vibrations at Renault Group, lets us in through the padded doors to theses temples of silence.

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...

The new acoustic experience is in the works. It will give rise to a new range of audio experiences: outstanding audio quality and more innovative services..

Stephane, Head of Acoustics and Vibrations, Renault Group 

SOUND BARRIERS


Go inside and hear the silence of the first anechoic chamber

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!"


Alain and Frank, Stephane’s co-workers preparing an acoustic test

In the centre of the room, surrounded by a hundred high-quality microphones, an All-new Megane E-TECH Electric draws all the attention of testers. "We measure the car’s sound-proofing in relation to noise generated by the engine, tyres, or anything else in the direct vicinity," explains Stephane. "This is where we fine-tune the car’s sound proofing, and work on all the noises that make up the user’s acoustic experience: sound of the car door, audio warnings and alarms, music, and more." Acoustic experts build up and assess the car’s entire sound architecture made of interior and exterior noises.

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.


Stephane and the All-new Renault Megane E-TECH Electric in the sound chambre

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


The Immunity chamber, where Megane E-TECH Electric is put through extreme electromagnetic testing

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," explains Xavier.


Xavier, Electromagnetic Compatibility Expert

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.


Every vehicle is put through its paces with these state-of-the-art testing tools

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 THE TEST CHAMBERS TO THE ROAD


The impressive Radio Frequency Chamber is where the car’s aerials are tested

Stephane takes us to one last room. "Watch your eyes..." he warns as he pushes open the heavy door. And rightly so, the room covers nearly 300 m² and is 11 meters high. The walls, floor, and ceilings are covered with large foam cones. It is the only completely anechoic chamber at the Aubevoye Technical Centre, and it is where experts test how all Renault vehicles, from ZOE to Master, perform when it comes to receiving waves.


Wave tests take place every day at the Aubevoye Technical Centre

All in all, the various anechoic chambers and analysis laboratories scattered throughout the sprawling Aubevoye Technical Centre host more than a thousand testing sessions each year. Many long months before they are unveiled – or are even given a name – future Renault vehicles spend days upon end in these sensory deprivation chambers, surrounded by invisible frequencies. Proof that a lot is at stake in these anechoic chambers, these little-known treasures of wave technology.

Enough to keep Stephane satisfied, as the light begins to dim around Aubevoye, and he leaves his ‘office’ to go home. Winding through the Normandy forests, he lowers his window, filling his car with the sounds of nature.