本文以實驗方法求得水中氣泡振動之阻尼常數，並與理論值比較。實驗方法主要是藉由水滴撞擊水面於水中產生單一氣泡，並利用水中聽音器量測氣泡之聲壓訊號。分析聲壓訊號可求得氣泡振動之阻尼常數。實驗所得阻尼常數將與理論解比較，以驗證目前文獻上有關氣泡振動阻尼理論之準確性。理論上，氣泡振動過程中能量損失主要有三種機制，分別為輻射阻尼、熱阻尼及黏滯阻尼。此外，當氣泡靠近自由液面時，氣泡之聲場會類似一偶極聲源 (dipole)之聲場，影響其輻射阻尼。若氣泡剛生成時為非圓球形時，也會有形狀振動模式。當形狀振動頻率與氣泡徑向振動頻率相同發生共振時，會產生額外的黏滯阻尼。本文氣泡振動阻尼常數之實驗值與考慮上述阻尼機制所得之理論值相較之下，相當吻合。此外，當氣泡半徑較大時，考慮形狀振動與徑向振動共振之黏滯阻尼，會使得理論值與實驗值較接近，但對較小氣泡而言，上述結果剛好相反。

This paper determined the damping constant of the bubble oscillation experimentally. The experimental damping constants were then compared with the theoretical values, for verifying the accuracy of the theories. The bubble was produced by impacting single water droplet on a water surface. An underwater monitoring system was set up for detecting the sound of the bubble. The damping constants were then determined from the measured bubble sound. Theoretically, the attenuation of a spherical bubble in radial vibration is due to the radiation damping, the thermal damping, and the viscous damping. When the bubble locates near the free surface, the radiated sound field from the bubble behaves like that of a dipole. Furthermore, if the generated bubble is not spherical, a shape oscillation mode exists. The resonance of the shape oscillation and the radial vibration induces additional viscous damping. The experimental data for damping constants were in good agreement with the theoretical values. It is also to note that for larger bubbles, the inclusion of the viscous damping due to the resonance of the shape oscillation and the radial vibration reduces the deviation between the theory and the experiment. However, for smaller bubbles, the results were on the contrary.

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