A micro-machined source transducer for a parametric array in air

Abstract

Parametric array applications in air, such as highly directional parametric loudspeaker systems, usually rely on large radiators to generate the high-intensity primary beams required for nonlinear interactions. However, a conventional transducer, as a primary wave projector, requires a great deal of electrical power because its electroacoustic efficiency is very low due to the large characteristic mechanical impedance in air. The feasibility of a micro-machined ultrasonic transducer as an efficient finite-amplitude wave projector was studied. A piezoelectric micro-machined ultrasonic transducer array consisting of lead zirconate titanate uni-morph elements was designed and fabricated for this purpose. Theoretical and experimental evaluations showed that a micro-machined ultrasonic transducer array can be used as an efficient source transducer for a parametric array in air. The beam patterns and propagation curves of the difference frequency wave and the primary wave generated by the micro-machined ultrasonic transducer array were measured. Although the theoretical results were based on ideal parametric array models, the theoretical data explained the experimental results reasonably well. These experiments demonstrated the potential of micro-machined primary wave projector.

A micro-machined piezoelectric flexural-mode hydrophone with air backing: Benefit of air backing for enhancing sensitivity

“…Taking into account the stress distribution in the radial direction, the piezoelectric layer was designed to be smaller than the diaphragm because electro-mechanical coupling is more effective when the piezoelectric layer covers a smaller area in the center of the diaphragm rather than the total area of the circular plate. [18][19][20] The main design parameters of the sensor discussed here are the silicon diaphragm radius r s , the thickness t s , the piezoelectric layer radius r p and thickness t p , and the backing chamber dimensions. The front of the diaphragm is exposed to the external medium through the housing, and the chamber is located on the opposite side of the diaphragm.…”

A Parametric Array Ultrasonic Ranging Sensor with Electrical Beam Steering Capability

“…With ultrasonic ranging sensors, electrical beam steering may enable ar eduction in the number of sensors required for navigational control of as ystem of mobile robots. The parametric array (PA) ultrasonic ranging sensor [1] has high spatial resolution due to its narrowbeam width; however, alarge number of these sensors are required to covern avigation overag iven angular region compared with ultrasonic sensors with awider beam width, which may increase the cost of the navigation system. Forthese reasons, electrical beam steering is particularly desirable with PA ultrasonic ranging systems.…”

“…Using this technique, the aperture of the source can be small compared with the wavelength of the generated sound [2]. The high directivity of the lower DFW generated by the PA makes it suitable for applications such as underwater sound navigation systems (SONAR) [ 3], high-resolution ultrasonic ranging acoustic navigation systems for mobile robots [1,4], and PA loudspeaker systems [5,6]. However, since aP Ae xploits anonlinear phenomenon, the suitability of electrical beam steering methods based on linear acoustics requires careful investigation.…”

Aluminum Nitride Ultrasonic Air-Coupled Actuator

“…In another ZnO work, Lee and Lee [18] reported an actuation response of 77 nm at a resonance of 54.8 kHz and 1 V pk for a circular microphone which is 2 mm in diameter. Lee et al [19] designed an array of circular diaphragms with a central PZT embossment for an ultrasonic ranging system using the parametric array effect. The authors reported two diaphragm designs with diameters of 1.2 and 1.42 mm and a thickness of 15 μm.…”