John Laurence Davy RMIT University Melbourne, Australia The directivity of the forced radiation of sound from panels and openings including the shadow zone John Laurence Davy RMIT University Melbourne, Australia

Situation of panel or opening From room to outside via opening or panel in (baffled) wall of room From outside to room via opening or panel in (baffled) wall of room From duct to outside via (baffled) duct end opening School of Applied Sciences

Directivity in infinite baffle Transmitted sound Finite opening or panel of length 2a θ Infinite baffle φ Incident sound Normal School of Applied Sciences

Directivity effect of finite width ka = 15 School of Applied Sciences

Radiation efficiency School of Applied Sciences

Diffraction due to finite baffle Sound Sound Normal Normal θ θ Rigid baffle length 2L Rigid baffle length 2L Sound incident on baffle Sound radiated from baffle School of Applied Sciences

Sound pressure doubling kL = 10 School of Applied Sciences

Small baffles at normal incidence School of Applied Sciences

Interpolation region p(90) = 1 p(0) p(90) = 1 School of Applied Sciences

Sound incident at angle  b m  g m Sound source b tan  m School of Applied Sciences

Incident sound intensity α = 0.3, b = 2 m, g = 4 m School of Applied Sciences

Directivity of duct sound source School of Applied Sciences

Diffraction into the shadow zone School of Applied Sciences

6 mm glass 60 degrees School of Applied Sciences

85 mm diameter duct 120° School of Applied Sciences

Conclusion The directivity of panels and openings excited by sound incident from the other side can be predicted using the model presented in this paper This two dimensional model agrees well with experimental results for both panels and openings The simple diffraction model and the angular weighting model work well School of Applied Sciences