Abstract
Our previous study has revealed that acoustic resonances have non-negligible effects on photoacoustic signals for a liquid sample confined in a thin tube. In this paper, we present numerical and experimental studies on the effects of tube hardness on the directivity of the generated photoacoustic signal. A thin glass capillary and silicone tube of 1 mm in diameter were tested using a pulsed light of 637 nm wavelength. Black ink was confined in the glass capillary and silicone tube as a photoacoustic sample material. In the glass capillary, acoustic resonance modes in the glass capillary were efficiently excited, and clear directivity was observed in the generated photoacoustic signals. On the other hand, little resonance was stimulated in the silicon tube because of the acoustic impedance matching between the sample and surrounding media, which resulted in the weak confinement of acoustic waves. The results suggest a possibility of characterization of the physical properties of thin tubes.
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