The Sound of Safety: Acoustic Sensors in Modern Vehicles

14-09-2023 | By Robin Mitchell

As cars become more intelligent, adding additional sensors only helps to improve situational awareness. However, one area that remains unheard of is acoustic sensors in vehicles, and researchers are now working on giving cars the ability to hear. What advantages could acoustic information give to vehicles, what exactly are the researchers developing, and how could this change the future of vehicles?

Image of a 3D rendering depicting autonomous electric vehicles utilizing artificial intelligence for self-driving on a metropolitan road.

What advantages could acoustic information give to vehicles?

When it comes to modern vehicles, there is no shortage of sensors, and they typically include multiple ultrasonic range sensors for parking and object detection, visual cameras for spotting traffic and pedestrians, LiDAR for accurate distance measuring between nearby vehicles for use with adaptive cruise control, and in some cases, RADAR which is used to detect traffic at long distances. By having multiple sensing technologies, it is possible for vehicles to operate in all weather conditions, creating a far safer driving experience for all drivers and pedestrians. 

However, even with all of these technologies, mistakes can still occur. One excellent example was a viral video demonstrating how a Tesla mistook an orange full moon as being an amber light at a traffic stop. Other more frightening examples typically show how vehicles fail to stop when pedestrians cross the road or decide to randomly turn into other lanes due to sensor fault. As such, no vehicle has yet reached full self-driving, despite numerous claims made by one famous automotive company whose CEO is convinced that self-driving is already here.

As such, adding more sensors can help vehicles distinguish between different data feeds, deciding what data is most likely to be the truth and what data to ignore. However, one sensor type has been mostly ignored by the automotive industry despite it being one of the most fundamental senses in human biology: acoustic.

When humans drive cars, they don’t just look at the road and make decisions based on that; the sound from the tyres against the road, the sound of emergency vehicles, and other cars beeping all contribute to said decisions. Thus, a vehicle fitted with such sensors could use acoustic data to try and determine the road conditions (via water splashing and slipping on ice), listen out for distant emergency vehicles, and react to vehicles that are about to collide with them.

Recent advancements in acoustic sensor technology have shown promising results. According to a piece of research news from the Fraunhofer Institute, tomorrow's vehicles will be equipped with a sense of hearing, enabling them to perceive sounds like bicycle bells, children playing, or sirens of approaching emergency vehicles. This development is not just about adding another sensor but about enhancing the vehicle's ability to make more informed decisions based on the acoustic environment around it.

Researchers developing acoustic sensors for vehicles

Recognising the importance of acoustic data in vehicles (for both drivers and autonomous systems), researchers from the Fraunhofer Institute for Digital Media Technology have started to develop both acoustic sensors for vehicles as well as an AI-based system that will be able to improve acoustic event recognition. While little information is available on the sensors themselves (as they are likely to build on existing technologies such as electret microphones), details were provided in their press release describing how such audio data can be beneficial in vehicles. 

The Fraunhofer Institute's initiative, known as "The Hearing Car", focuses on developing AI-based system solutions for acoustic event recognition near vehicles. Their research indicates that external noises, such as ambulance sirens or the sound of wet roads, can provide crucial information to drivers. Traditional vehicle sensors often fall short in detecting these sounds, which is where the intelligent acoustic sensor systems come into play. These systems aim to equip cars with a sense of hearing, working alongside other driver assistance systems to provide relevant data for driving manoeuvres or predictive maintenance.

One such example of how acoustic sensors could be beneficial in vehicles was the acoustic turn assistant, which involves acoustic sensors listening for any potential sources of sound in blind spots (such as other cars and pedestrians). Noises generated from the engine can also be used by acoustic sensors to detect objects, as reflected sounds can increase the apparent sound of a vehicle.

Another example of how acoustic sensors could be beneficial in vehicles presented by the press release is acoustic rear-view cameras. Simply put, instead of drivers having to open windows to hear if pedestrians are around, microphones located in the back of the vehicle can be used to increase situational awareness. For example, someone shouting at a driver to stop will be auditable to the driver, thereby allowing for faster reaction times and increased safety. 

Moreover, Fraunhofer IDMT in Oldenburg is also working on a novel concept: the integration of acoustic rear-view cameras. This technology, akin to having ears at the back of your car, offers drivers a unique advantage. Microphones strategically positioned on the vehicle and advanced software allow drivers to interact with the environment outside the vehicle without needing to lower windows. The research conducted at Fraunhofer IDMT in Oldenburg is centred around the precise recording and reproduction of ambient sounds in terms of their location. This functionality not only enhances driver awareness during various manoeuvres but also holds the potential to actively prevent accidents.

How could such sensors change vehicles of the future?

Installing acoustic sensors into vehicles may seem strange at first, but there are some very real benefits that can come with it. One such potential future feature in vehicles is early warning systems for emergency vehicles, whereby a chime or dashboard light engages when a distant emergency vehicle is heard. This can be especially important for drivers who have loud music, noisy children or are faced with treacherous conditions.

It is also possible that future vehicles will need to use such sensors to amplify external noises. As automotive manufacturers constantly try to reduce cabin noise (with the goal of improving the driving experience), noises that drivers need to hear are being reduced. Thus, external acoustic sensors combined with AI could amplify external noises while eliminating engine and traffic noise. 

Overall, acoustic sensors are undoubtedly going to start turning up in future vehicles, and their importance will increase as vehicle technologies such as noise cancellation and self-driving improve. 


By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation, developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.