Hidetomo Nagahara

Development of High-Sensitivity Ultrasonic Transducer in Air with Nanofoam Material

For a high-sensitivity ultrasonic transducer in air, it was considered that nanofoam be applied to its acoustic matching layer. Nanofoam is a porous material that is made by the sol-gel process. Since nanofoam has an extremely low acoustic impedance, it is effective for the acoustic matching layer of an ultrasonic transducer in air. In this study, we have fabricated an ultrasonic transducer that had two acoustic matching layers and estimated its acoustic properties. The two matching layers were made of silica nanofoam and porous ceramic. The sensitivity of the developed ultrasonic transducer was about twenty times higher than that of a conventional ultrasonic transducer in air.

P1M-8 Acoustic Properties of Nanofoam and its Applied Air-Borne Ultrasonic Transducers

Nanofoam is a porous material called drying gel or aerogel. Nanofoam has a low density and a low acoustic velocity. Because of these properties, it was considered that nanofoam can realize high performance air-borne ultrasonic transducer. We applied nanofoam to two types of ultrasonic transducers. One is a matching layer type of ultrasonic transducer (ML-UT), and the other is refractive propagation type of ultrasonic transducer (RP-UT). The sensitivity of ML-UT was twenty times as high as conventional. And we confirmed the basic operation of RP-UT on the basis of the observation of the propagation of ultrasonic in the peculiar direction and broadband characteristics. The frequency bandwidth of RP-UT was more than three times as wide as conventional

Novel air-borne ultrasonic sensor using nanofoam and a laser Doppler vibrometer

We propose a novel airborne ultrasonic sensor, using nanofoam and a laser Doppler vibrometer that can operate over a wide frequency range and provide high sensitivity. Nanofoam is a porous material made by sol-gel process and has low density, low elasticity, and extremely low acoustic impedance. These properties enable nanofoam to take in acoustic energy from ultrasonic waves. In addition, nanofoam has a good optical transmittance. Because optical detection can be much faster than detection period in the sound frequency range, it has been considered that a wideband ultrasonic sensor can be realized by the combination of nanofoam and laser measurement. In this report, we describe fabrication of the proposed sensor and determine its basic properties.

Airborne Ultrasonic Transducer

A high-sensitivity airborne ultrasonic transducer was produced by applying an aerogel to its acoustic matching layer, because an aerogel’s low density and low acoustic velocity result in extremely low acoustic impedance. We estimated the acoustic properties of this transducer and also fabricated an ultrasonic transducer having two acoustic matching layers made of silica aerogel and porous ceramic. The sensitivity of this novel ultrasonic transducer was found to be about 20 times higher than that of a conventional airborne ultrasonic transducer.