Design and realisation of a directional electric vehicle warning sound system

Abstract

The mandatory use of artificial warning sounds by electric vehicles at low speeds has generated concern over the resulting increase in urban noise levels. Systems have been proposed and tested that limit the vehicle’s environmental noise contributions by directing the radiated sound solely towards vulnerable road users. However, such solutions are often too costly to manufacture and maintain as they tend to feature loudspeaker arrays installed on the vehicle and exposed to the environment. This paper proposes a directional warning sound system for electric vehicles which uses an array of structural actuators attached to a panel of the vehicle’s body. The required warning sound is radiated by the vibrating panel and its directivity is controlled by adjusting the amplitude and phase of the signals driving the structural actuators. An analytical model is used to perform a simulation based parametric study of the proposed system, and this is then experimentally validated through measurements of a prototype using a flat metal panel. The effectiveness of the actuator array installed in an actual passenger car is then evaluated in a semi-anechoic environment. Directivity measurements are performed for different target zones using the array in a number of configurations on the vehicle’s body.