二胡是中國傳統民族樂器中最主要的擦弦樂器，近幾年已具有獨奏性，且逐漸成為目前最受歡迎的國樂樂器。但是二胡仍有許多缺點亟需改善，這些缺點包括：高音區之音量不足、高音時之雜音過多、穿透性不足、音域不夠寬廣、音色易受溫度與溼度影響、蟒皮來源取得不易、舊木料來源缺乏…等等。

本論文利用對聲音品質的瞭解，對二胡的聲音進行主觀的評估與客觀的量測分析，且製琴師也從經驗上提出一些建議，再配合修改後，制訂出一套評估二胡的樂音指標，例如：純淨度、均衡度、音量均衡度、尖銳度…等，以彌補傳統以上主觀的方法來評估二胡，藉以評價一把胡琴的好壞，並為其各項性能評定其等級，同時提供消費者在挑選胡琴時，能瞭解每把琴在音色上的差別，藉此挑選出一把適合自己使用的好琴。

由於影響二胡音色最主要的因素為琴皮與琴碼，故本論文選用數張不同特性（厚度、張力、密度與彈性等）的琴皮與不同材質的琴碼對二胡進行聲音量測，然後再利用已建立的二胡樂音指標來進行分析，並探討各項參數對於二胡在音色上之影響程度，同時有助於製琴師未來在製作上可依循的準則。

The erhu, commonly known by the West as the 'Chinese violin', is a two-stringed bowed instrument, capable of producing sad, mysterious, or joyful melodies. It belongs to the huqin family of Chinese instruments, together with the zhonghu, gaohu, and xihu. Recently, it has become more a solo instrument in many occasions and thus one of the most popular Chinese musical instruments. However, erhu still has a lot of shortcomings that need to be improved. These include insufficient sound power in the high pitch range, too much noise at the high pitch, the sound compass is limited, the tone color is easily influenced by temperature and humidity, python skins (python) are rarely acquired, and scanty old timber source.

This thesis investigated the sound quality of the erhu. First of all, we carried on subjective evaluation and objective measurement to analyze the sound of the erhu, and consult with the erhu maker's experience. Finally, we established one set of the objective indices of the musical sound of the erhu, such as purity, harmony, sharpness, and muffle, in order to evaluate the sound quality of the erhu, and grade its every performance.

According to an erhu-maker’s creating experience for many years, he found out that the python skin and the tiny bridge are the two main factors affecting the sound of the erhu. In this thesis, we selected several different characteristics (thickness, tension, density, and elasticity), python skin and bridge materials, and recorded the sound of the erhu, then used the erhu musical sound index to analyze, and probed into every parameter of the influence tone color of the erhu. In the same time, it can help erhu-makers to make a good erhu and instruct erhu-players how to choose an erhu of good quality in the future.

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