The impact of micromachined ultrasonic radiators on the efficiency of transducers in air

A Critical Step to Using a Parametric Array Loudspeaker in Mobile Devices

“…As discussed, Je et al reported that a properly designed pMUT may exhibit up to 80% radiation power efficiency [10]. Since the typical power consumption of micro loudspeakers (excluding amplifier power consumption) adopted in mobile phones lies in the range of 0.5~1.2 W [14], this may be set as the criterion for the feasibility of applying PA loudspeakers to mobile devices.…”

“…While the signal processing unit might consume only a small amount of power due to the well-developed digital microprocessors and peripheral chips, the power consumption of conventional power amplifier units usually depends on the output power it should generate. Hence, its power efficiency varies with the operating conditions [10]. However, the power consumption of the ultrasonic source transducer normally constitutes a large proportion of the total power consumption of a PA loudspeaker system, since the power efficiency is very low, at usually less than 10%.…”

“…In 2013, Je et al reported that an ultrasonic uni-morph-type radiator composed of a thin plate and a PZT layer, which is a type of piezoelectric micromachined ultrasonic transducer (pMUT), could radiate finite amplitude ultrasonic sounds efficiently at up to 80% power efficiency [10]. In the same paper, they also proposed a technique for constructing an array of pMUTs for generating ultrasonic sound beams with a wide frequency bandwidth and higher power efficiency.…”

“…In the same paper, they also proposed a technique for constructing an array of pMUTs for generating ultrasonic sound beams with a wide frequency bandwidth and higher power efficiency. They demonstrated that the fabricated array of pMUTs could generate PA audible sounds at low power consumption [10]. Hence, array pMUTs should be adopted as a component of the target PA loudspeaker for mobile devices such as notebook computers or, if the power consumption is low enough, smart phones.…”

“…This may constitute a limitation on the overall design. In this study, the power amplifier and signal processing unit were designed so that they could be built at a moderate cost, while the PA source transducer is designed and fabricated based on the design and fabrication methods for the pMUT array radiator developed by the research group [10].…”