How are cars set up for music and phone calls?

Are the audio systems in ŠKODA cars tested with sensitive acoustic measurement technology or with a trained ear? Both, of course. And more besides. Find out what the people in charge of setting up your car’s sound system do to make it sound great.

21. 6. 2022 Škoda World Innovation & technology

There are many ways to equip a car with high-quality audio technology today. For example, did you know that audio is calibrated differently for playback than for phone calls? “A car’s sound system is defined by the car’s class. A concept and strategy are then developed and used when putting together a set of speakers. They differ, for example, depending on whether an external amplifier is envisaged,” says Vlastimil Navrátil, coordinator of the reception and sound department at ŠKODA Technical Development.

One of the speakers in the latest version of the ŠKODA KODIAQ is housed in the door panel.

The basic version consists of a radio and speakers. An incomparably better experience is offered by “sound systems”, which deliver better sound through a higher number of speakers. ŠKODA offers two types: the simpler one found in lower-range models is called ŠKODA Sound and is developed by the carmaker itself. For the OCTAVIA, SUPERB, SUVs and electric cars, there is the Canton sound system. Developed together with a prestigious German manufacturer, Canton offers a three-band system for the front and a two-band system for the rear doors, and also includes a midrange speaker and a subwoofer.

These days, audio systems are usually controlled via the infotainment touchscreen, as in the ŠKODA ENYAQ COUPÉ RS iV, the Czech carmaker’s latest SUV.

A fight for every millimetre

The placement of the speakers is crucial for a good interior sound system. This is literally a matter of millimetres. “Our cars have an airy interior, so the door panels, for example, are made as thin as possible. That means there is not much space for various components – there are window adjustment mechanisms, door controllers and the requirement for space to store a plastic bottle. And then we need to fit speakers in there,” says Petr Rakušan, who is responsible for car speakers.

The speakers in the doors have to look good as well as sounding good.

The engineers try to ensure that the speaker is as close as possible to the mesh cover and does not interfere with the other “door equipment”. The stiffness of the sheet metal also plays an important role, which is why the speakers cannot be placed just anywhere. The woofer in particular needs the stiffest possible space, which is why it is placed in the bottom corner of the door near the hinge, so that the audio output does not leak into other parts. The midrange speaker is mounted directly on the door panel, i.e. on the plastic. “This is where it’s hard to find the best position. Here, too, we do a lot of tinkering to find the best placement and angle for the car’s occupants,” reveals Navrátil.

Phone Box is a practical new feature in ŠKODA cars that makes it easier to play content from a mobile phone.

The tweeter used to be in the doors as well, but it was moved to the A-pillar some time ago, which brought a significant improvement in reproduction quality. This is the optimal position, so the engineers are primarily concerned with the angle and optimising the grille covers so that the sound passes through them with no loss of fidelity before it reaches the interior space. For good visibility among other things, ŠKODA cars have very slim front pillars, so the speaker has to compete with the airbags and the sunroof drainage hoses for space. It’s a battle for every millimetre.

Cooperation and the struggle for position

The last type of speaker is the midrange one on the dashboard. ŠKODA directs the sound from it to the windscreen, from which it rebounds into the cabin. “This speaker significantly improves the listening experience and the naturalness of the sound – you hear the singer’s voice or other main sound element in front of you, not from the sides,” explains Tomáš Bambásek, the man responsible for sound systems.

The sound from the speaker concealed in the dashboard is directed at the windscreen.

Everything we have described makes it clear that the development process often has to contend with conflicting demands from different teams. To what extent, then, can the reception and sound department “lobby” for the best possible speaker placement? “We work closely with the designers, of course, and we can come up with the ideal position, but then a colleague who is responsible for, say, airbags’ gyroscopic sensors says he needs that position, and that naturally takes priority,” explains Rakušan.

The number of speakers for the various audio system levels is fixed. So you can choose a basic system for the front only or for all doors, or one of two sound systems. The top-of-the-range Canton system thus offers eleven speakers and a subwoofer with an output of two hundred watts. Depending on the car model, the total output of this system is up to 675 watts. In general, it is fair to say that parameters such as the number of speakers and music audio output are the same for all models the system is fitted in, with some minor differences.

Twelve-channel amplifier used in ŠKODA Sound.

Inside the amplifier’s control unit: circuit board, semi/conductors and microchips.

Sixteen-channel amplifier in the top-of-the-range Canton system.

This is the sixteen-channel Canton system amplifier.

In all ŠKODA cars, the amplifier processes the audio signal, converting it from digital to analogue and then amplifying it – this is the sixteen-channel Canton system amplifier.

Technology and the human ear

Now that we have the hardware sorted out, we need to get everything working properly. The first step is to take static measurements. This testing takes place in ideal conditions in the laboratory: the silence is not disturbed by outside noise. “We measure the car’s frequency characteristics to see how the various parameters are affected by the speaker grille cover or the placement of the speaker in the doors or on the dashboard. We try to achieve the most balanced sound character, i.e. the flattest curve possible. In other words, the input is the same as the output. So we don’t add bass, midrange, etc. The goal is to make the recording sound as identical as possible as the sound engineer mixed it in the studio,” explains Bambásek.

About eighty per cent of the parameters are calibrated in this way (with the Canton system, this part is done automatically), with the remaining fifth of the work done by ear. “Two of us get in the car and troubleshoot. We each have various reference tracks: we know what they are supposed to sound like in studio conditions and on good equipment, so we know what we want to hear. We try to get as close to that as possible in the car,” Bambásek explains.

The last phase of audio system testing takes place during the test drive on the testing polygon.

Once the static tuning is done, the car heads to the polygon. There, different road surfaces and speeds are simulated and the listening continues. The testers also take turns in the different seats, picking up on the subtle sonic nuances that emerge. It’s a very subjective thing, so it’s important for several people to take turns during the testing and listen to tracks they know like the back of their hand. This is the only way they can detect the slightest deviations. The Czech engineers admit that they often discover that they use the same reference tracks as their counterparts from other brands in the Volkswagen group. These tracks are simply well recorded.

Good sound at all speeds

All the versions of the audio systems offer GALA, a function that adjusts the volume of the sound according to the speed of the car, while at the same time slightly adjusting the frequency characteristics for the highest possible fidelity. For example, bass is added at low speeds and treble is reduced at higher speeds. This function masks the engine noise, aerodynamic noise and wheel noise that increase with speed. “We take measurements at different speeds and, based on the data we collect, we adjust the function to mask the noise the car makes. As a result, you basically don’t notice that the ambient noise level has increased and you don’t have to turn up the volume. Everything happens automatically.

Finally, the in-car audio is calibrated to make music sound as natural as possible inside the car.

Hello, can you hear me?

So far we’ve talked about setting up audio for entertainment, i.e. mostly for enjoying music. But Vlastimil Navrátil and his colleagues also have to deal with other considerations, such as hands-free calls on a connected phone, controlling the voice assistant Laura or the voice assistant on the phone. And last but not least, the emergency call module, which is activated in the event of an accident.

Laura can be commanded to commence navigation to a specified destination, play music of your choice or write dictated text messages, among other things.

These parameters vary depending on the technology used. For each of them, the quality of the audio signal, i.e. speech, is recommended or even required by a standard, and the characteristics are checked during the homologation of the car. The user has the option of using the classic Bluetooth hands-free or the more advanced technologies of Apple CarPlay or Android Auto, where data is transmitted via Wi-Fi or USB cable. “The main difference with the audio setup is that voice applications add another link in our chain: the microphone. Of course, microphones don’t just pick up the speaker’s voice, but all the sounds and noises in the car. Our main task in this area is to process the signal so that unwanted ambient noises and sounds are suppressed while the spoken word is understandable in all circumstances, which is very important in an emergency call, for example, when the car is damaged and the occupants may be injured,” explains Tomáš Choura, who is responsible for voice applications.

Apple CarPlay and Android Auto, technologies for playing music and other entertainment services, can be found in the ŠKODA ENYAQ iV all-electric SUV as well as other ŠKODA models.

The engineers conduct most of these tests acoustically, though some electric testing is still used. For hands-free, for example, nearly five hundred tests are carried out, measuring the basic parameters of the telephone channel such as level, distortion, frequency characteristics and feedback damping. More advanced tests check stability and intelligibility during simultaneous speech. “When we’re satisfied with these initial tests, we simulate driving the car in the lab and try to suppress the ambient noise, but not completely. We keep it at a low level to make it clear that the driver has to devote most of his attention to the driving. Of course, the voice must be clear and distinct and not drowned out by the background noise,” says Choura.

As with speaker testing, the final stage of testing takes place in real-life conditions on a test polygon. This testing stage irons out the last shortcomings, paying close attention to the ambient noise. The algorithms used are very robust and flexible, allowing them to adapt dynamically to a wide variety of driving conditions.

What does the future hold?

Given that, sooner or later, we will enter the age of Level 4 and Level 5 autonomous driving, when the occupants will want to have fun and not be disturbed by outside noise, it stands to reason that more and more systems will be developed to suppress outside noise. Some of the source information comes from external microphones, but noise from the chassis, wheel arches and so on also needs to be processed. This technology already exists, but it is still a very expensive solution that most car manufacturers cannot afford. So the future lies in finding a technically suitable and workable solution at a reasonable price.

Technology is being developed that will allow every car occupant to listen to their own audio, so children can listen to fairy stories while their parents put on their favourite AC/DC album.

Finally, one more insight into the future from the reception and sound team: imagine that every passenger in the car will be able to play their own sound without disturbing each other. A kind of zone will be created: one person can talk on the phone, another can listen to an audiobook and another can listen to Mozart or AC/DC. And they’ll have no problems sharing the same interior. Research and development is already underway and similar solutions do exist, but they are still in their infancy. The vision is nonetheless enticing.