The influence of finite and infinite wall cavities on the sound insulation of double-leaf walls.

Theories used to predict the sound insulation of double-leaf cavity wall systems are usually based on the assumption that the wall is of an infinite extent. To account for the effect of the finite extent of the wall, limiting the angle of incidence, a finite radiation efficiency model or the spatial windowing method is used in order to obtain realistic predictions. However, the effects of the finite extent of the cavity are often not included. This paper presents an extension of a finite two-dimensional cavity theory to include limp panels on each side of the cavity. It is shown that the oblique incidence mass-air-mass resonance can only occur for certain frequencies and certain angles of incidence. This is the reason why the infinite extent theories under-predict the sound insulation. The results of the predicted sound insulation agree with measurements when the wall cavity is empty. To obtain agreement when the cavity is full of a porous sound absorbing material, a flow resistivity of about one-fifth of the measured value has to be used. Use of the actual flow resistivity gives sound insulation values that are 10 dB too high.

[1]  P. P. Narang.  Effect of Fiberglass Density and Flow Resistance on Sound Transmission Loss of Cavity Plasterboard Walls , 1993 .

[2]  John L. Davy,et al.  Predicting the Sound Insulation of Walls , 2009 .

[3]  G. A. Work,et al.  Sound Transmission through Multiple Structures Containing Flexible Blankets , 1949 .

[4]  Philippe Jean,et al.  Measurement of the Sound Reduction Index as a Function of the Incidence Angle by Two Different Methods , 2006 .

[5]  John L. Davy.  The forced radiation efficiency of finite size flat panels that are excited by incident sound. , 2009, The Journal of the Acoustical Society of America.

[6]  Albert London,et al.  The Determination of Reverberant Sound Absorption Coefficients from Acoustic Impedance Measurements , 1950 .

[7]  Frank Fahy,et al.  Sound and Structural VibrationRadiation, Transmission and Response , 2007 .

[8]  J. Davy,et al.  The improvement of a simple theoretical model for the prediction of the sound insulation of double leaf walls. , 2010, The Journal of the Acoustical Society of America.

[9]  P. Narang.  Material parameter selection in polyester fibre insulation for sound transmission and absorption , 1995 .

[10]  T. E. Vigran,et al.  Predicting the sound reduction index of finite size specimen by a simplified spatial windowing technique , 2009 .

[11]  M. Heckl.  Einige Anwendungen des Reziprozitätsprinzips in der Akustik , 1964 .

[12]  R. A. Novak.  Sound insulation of lightweight double walls , 1992 .

[13]  Robin Wilson,et al.  Acoustic radiation from a plate into a porous medium , 2004 .

[14]  E. C. Sewell.  Transmission of reverberant sound through a single-leaf partition surrounded by an infinite rigid baffle , 1970 .

[15]  A. L'Esperance,et al.  Anisotropy effect in glass wool on normal impedance in oblique incidence , 1987 .

[16]  Jonas Brunskog.  The forced sound transmission of finite single leaf walls using a variational technique. , 2012, The Journal of the Acoustical Society of America.

[17]  L. Gagliardini,et al.  PREDICTING THE ACOUSTICAL RADIATION OF FINITE SIZE MULTI-LAYERED STRUCTURES BY APPLYING SPATIAL WINDOWING ON INFINITE STRUCTURES , 2001 .