Contributions aux études sur le couplage électroacoustique dans les espaces clos en vue du contrôle actif

The aim of this work was to analyze the global behavior of a loudspeaker exciting a room in the frequency band of its first modes, for the purpose of active control applications. First, the loudspeaker in free field was studied. The characterization of a loudspeaker on the base of equivalent circuits has been established, showing the preponderant importance of the load impedance, determined by near field measurements. Then, the steady state has been modeled and the study has been set on the characterization of the wall impedance, which determines the eigenfrequencies and the amplitude of their modes, as well as charge impedance. The latter which modifies the volume velocity compared with the one in free field, has been characterized. The previous results enable the precise computation of the pressure field in a closed space and excited by a loudspeaker in steady state, according to the wall impedance. For active control purposes, transitory sounds are particularly important, therefore the behavior of a sound field in a room excited by several parameterized sounds has been studied in the time domain. The room response to the source activation could therefore be modeled. This response consists of a free and a transitory state, both of which are qualified through coherent assumptions and observations. Through simulation and systematic experimentation, the loudspeaker-room system has been characterized for a stationary as well as for a transitory sound, revealing the constraints affecting modal active control. Many experiments showed the efficiency of modal active noise control. Observations presented the importance of low frequencies in the annoyance of airplane noise inside rooms. Directives have been given to install active noise reduction system. The main part of this work constitutes an electro acoustical knowledge basis to perform modal active noise control.

[1]  U. Ingard.  On the Theory and Design of Acoustic Resonators , 1953 .

[2]  Mark R. Avis.  Q-factor Modification for Low-frequency Room Modes , 2002 .

[3]  Frédéric de Coulon,et al.  Théorie et traitement des signaux , 1984 .

[4]  Tomas Salava,et al.  Acoustic Load and Transfer Functions in Rooms at Low Frequencies , 1988 .

[5]  Stephen J. Elliott,et al.  A Comparison of Three Methods of Measuring the Volume Velocity of an Acoustic Source , 1991 .

[6]  Zhu Xiaotian,et al.  Using optimized surface modifications to improve low frequency response in a room , 2004 .

[7]  G. Thomann,et al.  Aircraft sound measurements : The influence of microphone height , 2005 .

[8]  D. B. Keele,et al.  Low-Frequency Loudspeaker Assessment by Nearfield Sound-Pressure Measurement , 1974 .

[9]  Richard V. Waterhouse,et al.  Output of a Sound Source in a Reverberation Chamber and Other Reflecting Environments , 1958 .

[10]  T. Houtgast,et al.  The Modulation Transfer Function in Room Acoustics as a Predictor of Speech Intelligibility , 1973 .

[11]  Keith O. Ballagh,et al.  Optimum Loudspeaker Placement Near Reflecting Planes , 1983 .

[12]  R. Walker.  Equalization of Room Acoustics and Adaptive Systems in the Equalization of Small Room Acoustics , 1998 .

[13]  K. Kodera,et al.  A new method for the numerical analysis of nonstationary signals , 1976 .

[15]  P. Gonçalves,et al.  Time - frequency toolbox for use with MATHLAB , 1997 .

[16]  Neville Thiele,et al.  Loudspeakers in Vented Boxes: Part 1 , 1971 .

[17]  Allan R. Groh,et al.  High Fidelity Sound System Equalization by Analysis of Standing Waves , 1974 .

[18]  Richard H. Small.  Closed-Box Loudspeaker Systems-Part 2: Synthesis , 1973 .

[19]  Le Roux,et al.  Le haut-parleur electrodynamique : estimation des parametres electroacoustiques aux basses frequences et modelisation de la suspension , 1994 .

[20]  R F Job,et al.  Sources and effects of low-frequency noise. , 1996, The Journal of the Acoustical Society of America.

[21]  Patrick Flandrin,et al.  Improving the readability of time-frequency and time-scale representations by the reassignment method , 1995, IEEE Trans. Signal Process..

[22]  J. Robert Ashley,et al.  Experimental Determination of Low-Frequency Loudspeaker Parameters , 1969 .

[23]  Tomas Salava.  Low-Frequency Performance of Listening Rooms for Steady-State and Transient Signals , 1991 .

[24]  Bruno Fazenda,et al.  Low frequency room excitation using distributed mode loudspeakers , 2002 .

[25]  Matti Karjalainen,et al.  Modal Equalization of Loudspeaker-Room Responses at Low Frequencies , 2003 .

[26]  H. Sabine.  Room Acoustics , 1953, The SAGE Encyclopedia of Human Communication Sciences and Disorders.

[27]  Richard H. Small.  Closed-Box Loudspeaker Systems-Part 1: Analysis , 1972 .

[28]  Gerald R. Harris,et al.  Review of transient field theory for a baffled planar piston , 1981 .

[29]  Véronique Adam,et al.  Loudspeaker behaviour under incident sound fields , 2002 .

[30]  Véronique Adam.  Amplitude and Phase Synthesis of Loudspeaker Systems , 2000 .

[31]  Ronald M. Aarts,et al.  Approximation of the Struve function H1 occurring in impedance calculations. , 2003, The Journal of the Acoustical Society of America.

[32]  Hervé Lissek.  Les matériaux actifs à propriétés acoustiques variables , 2002 .

[33]  Allan D. Pierce,et al.  Acoustics , 1989 .

[34]  Yong Shen,et al.  Optimization of the locations of the loudspeaker and absorption material in a small room , 2004 .

[35]  Philip A. Nelson,et al.  Active Control of Sound , 1992 .