A micro audio directional system for portable multimedia devices is investigated as a novel loudspeaker which can provide privacy listening service. It can generates audible sound with high directivity in a narrow conical beam by an ultrasonic transducer array. A piezoelectric micromachined ultrasonic transducers (pMUT) array and a PZT ceramic wafer transducers array are presented respectively. The testing results of impedance, frequency response and sound pressure level characteristics are described and compared. A prototype with PZT ceramic wafer transducers array is constructed for mobile phone usage and its acoustic characteristics are measured. The experiment results indicate the feasibility of utilising the audio directional system with low power consumption and micro size in portable multimedia devices as well as in mobile phone.
['Xuesheng Li', 'Limei Xu', 'Leon Xu']
Micro audio directional system for portable multimedia devices