空氣中材料的聲學特性通常使用空氣阻抗管來測量。材料的反射係數、透射係數和吸收係數都可以利用不同類型的空氣阻抗管結合電腦軟體獲得。然而，隨著近年來國防工業的需求和環保意識的提高，水下噪音對海洋的影響越來越受到重視。因此，水下吸聲材料的開發已成為一個重要課題。測量水中材料的聲學特性，開發充水阻抗管，建立完整的測量程序是本研究的主要課題。
充水阻抗管可用於測量材料在水中的聲學特性。在實際環境中，不同深度下的靜水壓力變化可能會引起材料性質的變化，從而影響其聲學特性。為了研究不同靜水壓力對材料聲學特性的影響，本研究通過在阻抗管上安裝加壓設備，研製出一種加壓充水阻抗管。應用雙麥克風三參數校正（3PCM）方法獲得反射係數。
利用量測橡膠多孔材料來驗證實驗結果的重複性，同一實驗在同一天和不同天進行了3次。實測數據說明，同一天測得的吸聲材料反射係數幾乎相同，而不同天測得的結果只有微小的差異，從而驗證了實驗結果的重複性和所開發測量系統的可靠性。
在加壓阻抗管中測量矽膠、聚氨酯（PU）膠及不同厚度和不同壓力下的多孔橡膠材料的聲學特性。所得材料的水下聲學特性可為開發以橡膠材料為基體材料的吸聲材料提供基礎信息。
此外，為了全面了解材料的聲學特性，本研究中也研製了透射係數測量系統，並對多孔橡膠材料進行了測量。測量結果顯示良好的重複性，說明此一設計的可行性。

The acoustic properties of materials in the air are usually measured using air impedance tubes. The reflection, transmission, and absorption coefficients of materials can be obtained by using different types of air impedance tubes combined with the computer software. However, in recent years with the demand of the defence industry and the rise in environmental awareness, the impact of underwater noise on the ocean increasingly receives more attention. Therefore, the development of underwater sound-absorbing materials has become an important issue. Measuring the acoustic properties of materials in water, developing water-filled impedance tubes (WFIT), and establishing a complete measurement procedure were the main objectives of this study.
A water-filled impedance tube (WFIT) can be used to measure the acoustic properties of materials in water. In an actual environment, the varying hydrostatic pressure under various depths may cause changes in the material properties, and thus affecting its acoustic characteristic. So, in order to study the effect of the different hydrostatic pressure on the acoustic properties of materials, this study developed a pressurized WFIT by installing a pressurization equipment at the impedance tube. The two-microphone-three-calibration (3PCM) method was applied to obtain the reflection coefficients.
In order to verify the compatibility of experimental results, the proposed WFIT was used to measure the acoustic reflection coefficient of a porous rubber materials for three times on the same day and on different days. The measured data revealed that the reflection coefficients of sound-absorbing materials obtained on the same day were almost identical, while the results that obtained in various dates exhibited only slight differences, and thus the repeatability of the experimental results and the reliability of the developed measuring system were verified.
Acoustic reflection coefficients of silicon rubber, polyurethane (PU) rubber, and porous rubber material with different thicknesses and under various pressures were then measured in the pressurized impedance tube. The obtained underwater acoustic properties of materials might provide the basic information for developing sound-absorbing materials using the rubber material as the matrix material.
In addition, for a complete understanding of the acoustic properties of material, the WFIT has been further modified in order to make it capable of measuring the transmission coefficients through sound-absorbing materials. The measured sound transmissions through a porous rubber material revealed a good compatibility. Thus, the capability of the proposed WFIT for measuring both the acoustic reflection and transmission coefficients of materials was demonstrated.

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