In the car of the future, we will be sitting in our own sound bubbles

In a basement in Struer, advanced car sound concepts are being built and tested. The rig on the left is designed for accurate point cloud measurement of a car cabin, so that the sound systems can be tested on the computer before they are built into a real car. To the right, there is a dummy used to measure how passengers in the car affect the sound (spoiler for hitchhikers: it affects the sound zones too much). Illustration: Marianne Fajstrup

Imagine the whole family on a road trip. The driver is talking on the phone. The person in the passenger seat is listening to a podcast. In the back seat, one child is watching a movie, and the other one is listening to music. And no one is wearing headphones—all sounds come from the cabin.

It sounds like a recipe for disaster, ruining the holiday before even boarding the ferry, but there is peace and quiet since no one can hear the sound from the others’ speakers. It is only when someone says something that their voice reaches the others’ ears, so the whole family can talk just as if they were sitting at home at their dining table.

This car already exists—almost. It is a Lincoln Navigator, housed in a basement garage in Struer, with messy cables and active speakers built into virtually all available surfaces and a mannequin passenger equipped with extremely advanced measuring instruments.

There are still many technical challenges to overcome before the new sound system is ready to save the family holiday. But the concept was developed by Harman Automotive, which supplies music systems for half of our cars under a wide range of brands, so there is a lot of experience behind the ideas.

“Sound zones are kind of a guiding star for us. Being able to sit in your car seat and listen to music or radio news without disturbing the others in the car. You do not hear them. They do not hear you,” says Gorm Jørgensen, Senior Director at Harman Automotive in Struer and Head of the Development Team EPIC—Early Pursuits with Innovative Concepts, which devises and builds prototypes of car experiences with sound, light, movement, and design.

Noise Reduction Must Be Directed

The concept car is equipped with the full “Automotive Sound Field” solution with individual sound zones with full bandwidth for both music and conversation. Each seat has four speakers: two in the headrest and two located in front of the ears. There are cameras that continuously track the location of people’s heads as the whole concept of sound zones is built around the “Head Related Transfer Function” (HRTF).

Gorm Haldor Jørgensen next to the large Lincoln Navigator, which is packed with advanced sound equipment and secret test instruments behind the tinted windows. Navigator is the largest and heaviest SUV belonging to Ford’s luxury Lincoln brand, which also markets itself on the Revel sound system developed by Harman. And now, they are trying to go a step further. Illustration: Marianne Fajstrup

Our ears are so sensitive that a default setting does not work—the noise reduction and the sound must be constantly directed at and adjusted to the exact position of the ears.

Sound zones with active noise reduction and three-dimensional sound are the holy grail of sound developers, and Harman is not the only one trying to crack the code. A car cabin is a significantly more controlled environment than e.g. outdoor concerts, for which some companies are trying to create quiet zones. But it is still an extremely complex task that can hardly be solved with yet another of the incremental steps that sound development has been marked by.

However, there are also independent systems with less complexity in the concept car, which are more feasible, and which can be integrated separately by car manufacturers:

“Personal Communication Zones” for conversation and phone calls. “In Car Communication”, which has microphones on the front seat and amplifies the sound for the back seat. And “Kids’ Zone”, which creates a sense of calm in the back seat by enabling children to watch movies or play on their tablets without the sound reaching their parents in the front.

In addition to the sound one chooses to hear in the car, there are also natural sounds that need to get through the noise reduction, such as emergency vehicle sirens.

“It is relatively easy to let sirens through, but we have to collect samples from many countries because ambulances do not say “nee-naw” in the same way everywhere,” says Gorm Jørgensen, who is a civil engineer from DTU and has been involved in car sound systems from early on.

Other natural sounds provide necessary feedback about driving itself, such as the clicking relay sound of the turn signal and the engine revs. And if the car itself does not say anything, the sound system must help, and this provides an opportunity to embellish the reality a little. For example, Harman has developed a solution for a car with a V8 engine that switches off four cylinders when driving slowly and calmly.

“This is a very climate-friendly concept, but the sound is a significant part of the experience when it comes to the V8 engine, so we help generate the sound of the last four valves through the speakers,” says Gorm Jørgensen.

Since the two-tone car horns became illegal, there has not been much fun in developing sound for the outside of the car—most car horns formally have two tones, but they must sound at the same time.

However, since 2019, all electric cars sold in the EU have to be equipped with an “Acoustic Vehicle Alerting System” (AVAS), which must emit sound of at least 56 dB when the car is driving at less than 20 km/h—a “continuous, progressive sound”, which indicates how the car is moving, e.g. by increasing pitch with acceleration.

How Should an Electric Car Sound?

The most imaginative electric car sounds are thus excluded, so the neighbour’s Tesla does not emit the sound of clattering horses’ hooves when it backs out of the driveway—but at least you can hear it.

So far, there is no common understanding of how an electric car really “should” sound, and all electric car manufacturers are working with sound designers on solutions that are not just functional but support their brand. When Jaguar developed AVAS for its first electric car, the I-Pace, the focus groups preferred a futuristic sound. But when it was tested out in real life, it made pedestrians look up into the air—presumably looking for spaceships—instead of orienting themselves towards the electric car on the road.

The car for the slightly more distant future is currently only built of plywood. Here in the dark, sound and image systems are tested for fully self-driving cars, in which all seats are passenger seats. If no one needs to keep their eyes on the traffic, the full focus can be on supplementing the audio experience with video screens and light panels. Illustration: Marianne Fajstrup

Harman provides the AVAS solution “Electronic Sound Synthesis”, which sends directional sound from speakers both in front and in the rear to warn pedestrians and cyclists.

“The car manufacturers will offer a number of sounds so that users can choose how their electric car draws attention to itself,” says Gorm Jørgensen.

Before the new sound concepts are built and tested physically, they can be tested with an acoustic simulation of the sound fields in the car, which is created with a microphone array that provides a detailed point cloud measurement of the car. Like much of the other test equipment in the Harman basement, it looks like a Storm P. invention, but it is costly proprietary technology and one of the reasons why the basement garage does not have windows—and why Ingeniøren is not allowed to take close-ups. The second reason are regular stays of brand-new car models for which Harman must develop sound systems before they are presented to the public.

Harman International took over B&O Automotive in 2015, and today Harman Automotive supplies sound systems under several brands and develops solutions in collaboration with a number of car manufacturers. This is why in the large meeting room, there are two Lamborghini car doors, and there are side panels of different designs hanging on the walls. Mostly to be able to distinguish between the individual brands, but appearance is also relevant for the sound, and LED lights are increasingly used both as part of the design and to guide the operation of the system.

“Staging is important. The appearance of the speakers is definitely relevant in the assessment of sound quality, and we are also working on integrating interior lighting into the sound experience,” says Gorm Jørgensen.

In collaboration with B&O, they are working on a prototype, BeoSonic, for intuitive operation of the car’s sound system, reminiscent of the operation of mood lights: a dot of light is dragged across a circle to adjust between Energetic and Relaxed on one axis and Bright and Warm on the other axis. The effect can be increased or lowered by expanding or shrinking the size of the dot with two fingers. The colours around the circle are linked to the mood and are also displayed on the speakers.

In another demo car in the basement, a TV is built into the roof to support the sound in the cabin with visual cues, and although it currently must be taken into account that the driver has to be aware of the traffic, work is also being done on the complete experience in fully self-driving cars, where everyone is sitting in a passenger seat.