一般而言，車輛於高速行駛、引擎高速運轉或是行經粗糙路面時，往往造成車內噪音提高而掩蓋音響之訊號，本研究以聲學理論、數位訊號處理和即時控制的技術做為演算法的主軸，利用LabVIEW 7.1軟體設計即時控制的演算程式，再結合量測、控制用的硬體設備建立一套即時音量控制系統，這個系統能偵測車廂內環境的訊雜比，於背景噪音提高時，自動補償音響音量，使車內成員隨時皆可聽到清晰度良好之音樂。

本研究擷取了主要的噪音源音檔作為實驗環境噪音源，並分析其頻譜特性，以訂定控制演算法的取樣參數；以人耳聽覺的實驗方式定義出合理的訊雜比門檻值作為控制指標；採用音響聲源及車輛噪音源分別作為實驗環境中訊號及雜訊的來源，以兩個B&K 4188麥克風做為感測器，透過實驗求出兩者的轉移函數以定義兩麥克風的頻率響應關係，於控制演算法中讀取此資料矩陣，則可分離出駕駛座位置樂音及噪音的比例。最後整合控制軟體與硬體設備，比較不同環境下的控制效果，實驗結果證明了此系統已達即時控制的目的，並能保有原始樂音品質，確定了研究構想的可行性以及演算邏輯的正確性。

Generally Speaking, as a car is driven on rough roads or at a high speed, it would increase vehicle noise and mask the audio signals. In order to improve the sound quality for human hearing under dynamic conditions, this research establishes a real-time autorange volume control system which could detect the S/N ratio of the environment and compare with the threshold of S/N ratio defined by experiment then compensate for the output magnitude of the music signal.
The control algorithm compiled by LabVIEW 7.1 programming language depends on the basis of acoustics, DSP and real-time control technique. This research also collects and analyzes the major vehicle noises such as Road Noise, Engine Noise and Wind Noise and adopts the mp3 music files as the signal source. The data acquisition parameters depend on the characteristics of the noise source and signal source. So the system only processes the noise and signal sources fewer than 3 kHz.
The system is set up in lab and use two B&K 4188 microphones as the sensors. The relations of the two sensors are defined by their transfer function. The fact shows that the autorange volume control system could correct the output music signal immediately and keeps the great sound quality. This research could confirm the accuracy of the control algorithm and the feasibility of the concept.

[1]U.Widmann,J.Hobelsberger, “Simulating hearing sensations with a digital
measurement system for applications in automotive”

[2]S.F. Boll,“Suppression of acoustic noise in speech using spectral
subtraction,”IEEE Trans. On Acoust., Speech, Signal
Proc.,vol.ASSP-27,pp.113-120,April 1979.

[3]Robert Wm.Rieder“Low Frequency Design Considerations for Automotive Audio
System”SAE 950181

[4]Jan-Paul F.Huyser,Darby Hadley, “Intelligent Audio Amplifier”SAE970261

[5]Shinichi Ohki,Fumiyasu Konno,and Sumio Ishihara, “New Acoustic
Feedback System”SAE 950184

[6]Shinichi Ohki,Fumiyasu Konno,Yoshio Nakamura,Sumio Ishihara,and Toshihiko
Ohashi, “New-AFB Automotive Sound System”SAE960197

[7]Jan-Paul F.Huyser,Darby Hadley, “Self Adaptive Speaker System for
Automotive Sound”SAE 2000-01-0074

[8]Shinichi Maruyama, Junichi Aoki,Masanori Furuyama, “Application of a
reciprocity technique for measurement for acoustic transfer functions to the
prediction of road vehicle pass-by noise”ELSEVIER 1996.

[9]蕭子健．王志昱．儲昭偉，虛擬儀控程式設計LabVIEW 7X，高立
圖書有限公司，94年7月5日初版二刷。
[10]蔡國隆‧王光賢．涂聰賢，聲學原理與噪音量測控制，全華科技
圖書股份有限公司，2005年4月初版一刷。
[11]莊謙本，汽車音響，全華科技圖書股份有限公司，74年8月初版。
[12]木田康雄，現代音響科學(SOUND Theory and Practuce)，復漢出
版社，76年1月出版。
[13]劉成群,張超群,“汽車振動與噪音”，新文京開發出版有限公司，91
年1月初版