Investigation of a directional warning sound system for electric vehicles based on structural vibration

Warning sound systems for electric vehicles with advanced beamforming capabilities have been investigated in the past. Despite showing promising performance, such technologies have yet to be adopted by the industry, as implementation costs are generally too high and the components too fragile for implementation. A lower cost solution with higher durability could be achieved by using an array of inertial actuators instead of loudspeakers. These actuators can be attached directly to the body of the vehicle and thus require minimal design modifications. A directional sound field can then be radiated by controlling the vibration of the panel via adjustments to the relative magnitude and phase of the signals driving the array. This paper presents an experimental investigation of an inertial actuator-based warning sound system. A vehicle placed in a semi-anechoic environment is used to investigate different array configurations in terms of the resulting sound field directivity and the leakage of sound into the cabin. Results indicate that the most efficient configuration investigated has the actuators attached to the front bumper of the vehicle. Using this arrangement, real-time measurements for different beamformer settings are performed to obtain a thorough picture of the performance of the system across frequency and steering angle.