有鑑於演奏者或製琴師經常以「亮不亮」來描述琴音，然而目前已建立的二胡的樂音指標中（純淨度、渾厚度、HLT音量均衡度與HLC尖銳度）並無亮度指標可供評量，故本研究延續先前樂音指標之建立，找出較「亮」的琴音與2000~8000Hz頻帶之音量多寡有關，進而訂定出二胡之亮度樂音指標。另外也嘗試比較Zwicker響度均衡度指標與原有HLT音量均衡度指標間的關係；同時也將Zwicker銳度指標與原有HLC尖銳度指標作比較與說明。

本研究亦探討各種客觀因素對二胡音質的影響。在時間因素方面，多數的胡琴之純淨度會隨著時間增加而變得愈差；在濕度因素方面，多數的胡琴在濕度約40%時之整體表現較在濕度70%時為差；琴皮施以浸泡處理時，其渾厚度（低頻）與純淨度之表現均較佳；琴皮缺陷時，會使得整體表現變差，尤其低頻音量之比重過多，使得聲音聽起來的感覺非常「悶」。

另外，也以樂音指標來評價四種不同地方特色琴在音色上之表現，得知上海琴的整體表現較佳，北京琴的整體表現適中、而蘇州琴與改良前李氏琴的整體表現均較差。最後，探討改良前後李氏琴在音質上的差異，得知改用黃色網紋蟒皮之改良後李氏琴的純淨度與尖銳度均能顯著提昇，使得其整體表現較改良前為佳，甚至於優於上海琴。

In consideration of the fact that musical performers or makers often describe the musical sound with ‘Brightness’, however, currently there are not established musical indices of brightness for evaluation for Erhu, so this research continues previous establishment of musical indices to discover bright musical sound relating with the quantity of 2000~8000Hz frequency band and then establish Erhu’s musical indices of brightness. Also, this research manages to compare the relationship of indices between Zwicker loudness balance and original HLT loudness balance. At the same time the indices of sharpness of Zwicker and indices of sharpness of original HLC are compared and explained here.

This research also probes into the effects of different objective factors to Erhu’s sound quality. In the factor of time, mostly the clearness of Erhu’s sound turns worse as time goes by. In the factor of humidity, most Erhu’s perform worse with the humidity of 40% than humidity of 70%. The performance of Low Frequency and Clearness are better when giving the Erhu skin soaking treatment. Entire performance turns worse when Erhu skins got defective; especially the ratio of low frequency sound is too high. It sounds muffled.

In addition, this research evaluates performance of sound quality of featured Erhu’s from four different districts with musical indices. The entire performance of Shanghai Erhu is better while Beijing Erhu is OK. And SuZhou’s and unimproved Lee’s are worse. In the end, this research studies the variation of the sound quality of unimproved Lee’s Erhu and improved one and comes out the conclusions – Improved Lee’s Erhu which uses reticulated python-skin got obviously increased by ‘brightness’ and ‘Sharpness’ and entire performance is also better than unimproved one and even better than Shanghai Erhu.

[1] Hutchins, C. M., Research papers in violin acoustics, 1975-1993: with an introductory essay, 350 years of violin research, Published by the Acoustical Society of America through the American Institute of Physics, New York, 1997.
[2] Schelleng, C. J., “The violin as a circuit,” Journal of the Acoustical Society of America, c, pp. 326-338, 1963.
[3] Hutchins, C. M., “The acoustic of violin plate,” Scientific American, Vol.35, No.3, pp. 170-186, 1981.
[4] Roberts, G. W., Finite Element Analysis of the Violin, extract from Vibration of shells and their relevance to musical instruments, section of a doctoral
dissertation, University College, Cardiff, Wales, UK, 1986.
[5] Dünnwald, H., “Deduction of objective quality parameters on old and new violins,” J. Catgut Acoust. Soc. 2d ser, Vol.1, No.7, pp. 1-5, 1991.
[6] 鄭德淵，中國樂器學，生韻出版社，1984。
[7] 鄭德淵，音樂音響學（上冊），樂韻出版社，1981。
[8] 林昱廷，南胡空弦弦長的科學分析研究，學藝出版社，1995。
[9] 林昱廷，中國傳統樂器聲學特性之分析研究，行政院國家科學委員會專題研究計劃成果報告，1997。
[10] 林昱廷，南胡聲頻之研究與樂器改良計劃，行政院國家科學委員會補助專題研究計劃成果報告，2001。
[11] 田英志，二胡樂音之聲音品質與狼音改良，台灣科技大學機械工程研究所碩士論文，2004。
[12] 莊肯堯，二胡樂音指標之建立與蟒皮對於音色之影響，台灣科技大學機械工程研究所碩士論文，2005。
[13] Fletcher,N.H.,and Rossing, T.D.,The Physics of Musical Instruments,
Spring,New York,1998.
[14] David,M.H., and James,A.,Acoustics and Psychoacoustics, Focal Press, Boston,2001
[15] Zwicker, E., and Fastl, H., Psychoacoustics: Facts and Models, Springer, New York, 1999.
[16] 蔣再華、李蘇民、鄭伯順、黃嘉若與余秀敏，『規劃建立主觀音聲音品質評估系統』，電信研究季刊，第十九卷，第四期，第441~453頁，1989。