Browse Publications Technical Papers 2018-01-1550
2018-06-13

Experimental and Numerical Study on Speaker Design of Active Pedestrian Alerting System (APAS) in Hybrid and Pure Electric Vehicles 2018-01-1550

APAS refers to a low speed sound warning system of electric vehicles, which emits alerting sound only to target pedestrians by sound focusing techniques with array of speakers and object detective camera. In the present study, experimental and numerical investigations are conducted in designing speaker part and array of APAS with consideration of three main performance matrices; HEV/EV warning sound regulations in Europe and U.S., pedestrian awareness, and driver’s noise comfort. The present APAS speaker consists of back enclosure, wave guide and front grill. Each of these components plays an important role for characterizing frequency emphasis and sound directivity. The main impedance frequencies of the speaker are determined by considering warning sound regulations and also by analyzing acoustic frequency response at in/outside of a vehicle. As a result, the dimensions of the speaker components are designed to be capable of satisfying warning sound regulations and to radiate more pedestrian perceptive sound with smaller noise influence to a driver. The test and simulation results of the actual speaker prototype are found to agree well with these original intentions. The simulation results also have shown that dimension of the wave guide is very important tuning factor on directivity performance as well as mid-frequency impedance determination. Lastly, the installation effect of 6-speaker array is investigated in three different candidates of placement through acoustic simulations. The results of the simulations are verified through a vehicle test for better sound focusing performance with the minimum acoustic dead zones.

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