以雷射測距儀製作古典吉他脈衝響應以應用於音色轉換;Impulse response generation of classical guitars using laser displacement sensor for tone transfer

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題名:	以雷射測距儀製作古典吉他脈衝響應以應用於音色轉換;Impulse response generation of classical guitars using laser displacement sensor for tone transfer
作者:	葉哲旭;YEH, CHE-HSU
貢獻者:	光電科學與工程學系
關鍵詞:	脈衝響應;轉移函數;古典吉他;麥克風;雷射測距儀;音色還原;impulse response;transfer function;microphone;classical guitar;laser displacement sensor;tone transformation
日期:	2023-08-01
上傳時間:	2024-09-19 15:47:35 (UTC+8)
出版者:	國立中央大學
摘要:	本研究主旨係在探討使用激發古典吉他後擷取的脈衝響應以及頻譜資料，製作出能將兩把古典吉他音色轉換的轉移函數。我們使用不同激發方法以及感測器來擷取古典吉他之脈衝響應以及頻譜資料，並使用頻譜相除法製做出能轉換音色的轉移函數，並對兩把古典吉他完成音色轉換。研究中使用了三種激發方法來擷取古典吉他的脈衝響應以及頻譜資料，分別是垂直面板撥絃法、氣球脈衝聲波法和喇叭播放白噪音法。透過比較這些方法，我們得出了以下結論。首先，比較了使用三種激發方法製作的轉移函數。結果顯示，這些方法都能成功激發出古典吉他的音孔共振頻率。但在觀察頻譜時，氣球脈衝聲波法和喇叭播放白噪音法出現了高頻噪聲過大和非目標還原音色的頻率峰值。由於垂直面板撥絃法的頻譜呈現較低的噪聲，也較適合用於激發古典吉他。其次，我們比較麥克風和雷射測距儀兩種感測器擷取的脈衝響應以及頻譜資料所製作的轉移函數。在同樣使用垂直面板撥絃加總法時，不論是麥克風擷取還是雷射測距儀製作的轉移函數，都能成功轉換古典吉他的音孔共振頻率峰值。但麥克風製作的轉移函數在還原音孔共振頻率的能量上相對較弱，而雷射測距儀製作的轉移函數能夠更好地還原音孔共振頻率。最後，我們使用互相關和重疊積分的結果，來評估麥克風和雷射測距儀所製作的轉移函數的音色還原效果。結果顯示，雷射測距儀所製作的轉移函數具有較高的互相關性和重疊積分值，這表明雷射測距儀所製作的轉移函數能夠更準確地還原古典吉他的音色。;The main objective of this study is to generate the transfer function capable of transforming the timbre of two classical guitars using the impulse responses captured after exciting the classical guitars. We employed different excitation methods and acoustic sensors to capture the impulse response of the classical guitars and to generate the transfer function for tone transformation between two guitars. Subsequently, we applied this transfer function to achieve tone transformation between the two classical guitars. Three excitation methods were used to capture the impulse response of the classical guitars: vertically plucking, balloon pulse sound wave, and white noise excitation by loudspeaker. Through a comparison of these methods, the following conclusions were drawn: Firstly, a comparison was made between the transfer functions produced using the three excitation methods. The results demonstrated that all these methods were successful in exciting the air resonant frequencies of the classical guitars. However, when observing the spectral data, the balloon pulse sound wave and white noise excitation by loudspeaker exhibited excessive high-frequency noise. The vertically plucking method, on the other hand, showed the lower noise levels and was more suitable for exciting the classical guitars. Secondly, we compared the transfer functions created from the impulse response captured by two different acoustic sensors: microphone and laser displacement sensor. The transfer function generated by both methods can successfully transform the air resonant frequency peaks of the classical guitars. Finally, we evaluated the tone restoration by the transfer functions produced by the microphone and the laser displacement sensor using the cross-correlation and the overlap integral. The results indicated that the transfer function generated by the laser displacement sensor exhibited higher cross-correlation and overlap integral values, suggesting that the use of the laser displacement sensor could restore more accurately the tone of the classical guitars.
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