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  • 學位論文

虛擬麥克風於車廂噪音控制的應用

Application of Virtual Microphone for Noise Control in A Car Cabin

指導教授 : 劉興華
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摘要


本研究是將虛擬麥克風技術運用在模擬行駛的車子中,目的是將不是放置在耳朵的參考麥克風聲壓,運用演算法估測到駕駛者耳朵附近虛擬麥克風的聲壓,藉由檢測麥克風來檢測估測是否準確,若估測準確,將非常有助於耳廓的局部主動式噪音控制的效果。實驗步驟第一步比較演算法;第二步以單顆揚聲器在車廂播放原音訊和低通濾波的音訊,並調整取樣頻率錄音,藉由調整濾波器長度階數來收斂誤差;第三步以實車四顆揚聲器做實驗,實驗方法同第二步;第四步考量駕駛者駕車時,頭部並不會固定不動,所以麥克風隨著人偶頭部移動位置,藉由調整濾波器長度階數以及距離來觀察誤差變化;第五步為將參考麥克風擺在車廂內不同位置,以參考麥克風和虛擬麥克風之間不同距離,參考專利把參考麥克風擺在車廂內不同位置,目的為找出參考麥克風在車廂內的適用位置。實驗結果可知揚聲器播出經過濾波後的音訊,經由參考麥克風經過演算法後耳廓的虛擬麥克風訊號和檢測麥克風訊號間的誤差,並非演算法濾波器長度階數越高,誤差就比較小;而參考麥克風與檢測麥克風距離若太大,演算法計算出的虛擬麥克風和檢測麥克風間的誤差會提升很多,雖然近距離誤差比較小,但是若音訊過於複雜,參考麥克風經由演算法所估測出來的虛擬麥克風值,也會和檢測麥克風間的誤差增加。

並列摘要


The purpose of this study is to estimate the sound pressure perceived of driver by applying virtual microphone technique to the noise simulation of a driving vehicle. If the sound pressure is estimated correctly, it may be useful for local active noise control at a pinna. Experimental procedures are as following, first step is to choose different algorithms. Second step is recording both original and low-pass filtered noise played by the speaker in the back seat with different sampling frequency, errors will be convergence by adjusting filter length order. Third step is the same as the second step except the noise is played by the four car speakers. Fourth step, study the influence of the filter length order and microphone position on head movement of the driver. Fifth step is to investigate the choice of the different distant in the cabin positions of physical microphone by a patent. Experimental results show the error between the virtual microphone and the detective microphone at a pinna is not necessary to reduce by increasing the filter length order. Also the error will increase when the distance between physical and virtual microphone become larger by the detective microphone check. Although short distant error is reduce. However if sound is complex after physical microphone record and input to algorithm, output virtual microphone the error is increase by the detective microphone.

參考文獻


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