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A micromachined efficient parametric array loudspeaker with a wide radiation frequency band.
Yub Je1, Haksue Lee2, Kyounghun Been1
1Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang, Kyungbuk 790-784, South Korea.
The Journal of the Acoustical Society of America
|April 30, 2015
Summary
This study developed a high-efficiency parametric array (PA) loudspeaker using an array of piezoelectric micromachined ultrasonic transducers (PMUTs). The novel design achieves a wide bandwidth, enabling efficient private listening applications.
Area of Science:
- Acoustics
- Transducer Technology
- Materials Science
Background:
- Parametric array (PA) loudspeakers offer private listening capabilities by generating directional sound.
- High power efficiency and wide frequency bandwidth are crucial for practical PA loudspeaker applications.
- Piezoelectric micromachined ultrasonic transducers (PMUTs) are suitable compact and efficient sources for PA systems.
Purpose of the Study:
- To investigate the use of a PMUT array for creating a high-power-efficiency, wide-bandwidth PA loudspeaker.
- To determine the maximum achievable radiation bandwidth for a PMUT-based PA driver.
- To enhance the bandwidth of a PA loudspeaker using dual-resonance PMUT arrays and out-of-phase driving.
Main Methods:
- Calculated the maximum radiation bandwidth of the PA driver.
- Designed a PMUT array with two distinct resonance frequencies (100 kHz and 110 kHz).
- Employed out-of-phase driving techniques for the dual-resonance transducer array to broaden bandwidth.
Main Results:
- The fabricated PMUT array achieved a power efficiency of up to 71%.
- A ±3-dB bandwidth of 17 kHz was observed for directly radiated primary waves.
- A bandwidth of 19.5 kHz (500 Hz to 20 kHz) was achieved for difference frequency waves with equalization.
Conclusions:
- A PMUT array can effectively function as a high-efficiency, wide-bandwidth PA loudspeaker source.
- Dual-resonance frequencies and out-of-phase driving are viable methods for increasing PA loudspeaker bandwidth.
- The developed PMUT array shows promise for advanced information technology devices requiring efficient directional audio.
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