基於數位波導與三質量模型之吉他琴身轉換

Abstract

傳統上以數位波導為基礎之吉他聲音合成在合成吉他琴身時，會使用數位濾波器來模擬吉他的脈衝響應。儘管我們可以去改變數位濾波器的係數抑或參數，其改變與實際物理性質的關聯並不直接。相對於此，三質量模型提供了質量、面積、勁度等與實際物理性質相關的參數可供調整。因此，本研究提出以三質量模型合成琴身，而數位波導合成琴弦來做為吉他琴身轉換的聲音合成架構。為了評估此方法是否有效，我們轉換兩把大小、材質不同的吉他，並且與 warped IIR（WIIR）濾波器相比較。聽測的結果顯示使用三質量模型的吉他聲音相似度及可接受度皆高於使用 WIIR。而未來若要改良此合成架構，也許可以從琴弦和琴身之間的耦合效應著手。

The three-mass model is used to replace the digital filters for guitar body synthesis; with inverse filtering technique, we are able to take out the body response, change the parameters, and then embed the modified one back. To assess the ability of body transformation, two different guitars—Baby Taylor BT1, the smaller one, and Furch F-24-SR—were transformed between both using three-mass model and warped IIR (WIIR) filter, while the guitar strings are modeled by digital waveguides. The results show that the three-mass model has higher similarity and acceptability than WIIR. However, the transformations are incomplete. To improve the result, one may start with taking the string–body coupling into account.