3D SOund ReproduCtion using sound-Emitting surfaces in cars – SOURCE

In the foreseeable future, the adoption of multifunctional car structure (MCS) will offer the potential to radically upgrade the abilities of vehicles in terms of ecological requirements emerging from the social and legal environment. Integrating car structures with functional systems that monitor structural integrity and aging, change shape at local level, act as sound sources and tackle noise vibration harshness issues will eliminate many of the weight, volume, and signature penalties associated with the current approach of designing, manufacturing and maintaining vehicles and functional systems separately. Current cars already have a structure optimized to have low weight without reducing the required performances. However, by means of MCS structural components can be further reduced in weight without compromising resistance, crash and fatigue performances while still offering more advanced functionalities. One type of MCS that appears as very promising and which we propose to investigate in this project is a Load-bearing Loudspeaker Structure (LLS). A LLS refers to structures that are equipped with active elements such as piezoelectric elements that allow for sound spatialization and noise and vibration control. In terms of integration, LLS structures may easily be retrofitted to existing car frames (interior or exterior) or incorporated within new platforms.
As acoustics plays a key role in automotive design, a widespread use of LLS will enhance vehicle security and comfort. Indeed, on the one hand, auditory warnings are vital in the automotive world in attracting attention and conveying information to the driver. Auditory warning alerts reduce the distraction of the driver from his primary driving task and therefore enhance the safety. Spatial restitution of warning signals is furthermore directing the attention of the driver directly towards the danger. It provides a more intuitive way of conveying information and better interaction with other human-machine interfaces. We intend to excite these surfaces to generate and spatialize auditory warnings. On the other hand, wave field synthesis with a reduced number of loudspeakers will allow us to produce more realistic sound inside the passenger cabin, which is becoming increasingly important in entertainment systems in partially autonomous and autonomous cars.
In summary, this project proposes to functionalize the surfaces present inside the passenger cabin of a car in order to enhance vehicle security and comfort by addressing the following scientific and industrial issues: Based on a system and user requirements evaluation the figures of merit of such a new class of loudspeaker will be determined. Then, special low energy piezoelectric transducers will be designed that allow covering the whole audio frequency spectrum. A main research area will address the high amplitude requirements at low frequencies. In order to compensate for sound panel non-linearities, active control strategies for sound improvement and surface vibration mitigation will be designed. Those surface loudspeakers will be integrated into a test car, once they achieved sufficient robustness and sound quality. Equalization and compensation methods will be applied to guarantee perfect equilibrium of the sound. In a first step, the efficiency of the whole system will be deduced from user-centred evaluations compared to a traditional loudspeaker set-up. In a second step, after several iterations a more complex sound scenario based on 3D sound field reconstruction will be implemented into the test car. Qualitative ratings of this second system will be extracted from a second user study.