Analytical and experimental study of single frame double wall

Transcription

1 Analytical and experimental study of single frame double wall C. Guigou-Carter and M. Villot Center for Building Science and Technology Acoustics and Lighting Department Paper ID 203 Analytical and experimental study of single frame double wall PAGE 1

2 INTRODUCTION Lightweight single frame double walls are common solutions for partitioning in dwellings The mounting frame corresponds to structural connections and is associated to a structural path having great importance on acoustic performance Model based on wave approach and SEA approach is presented Studs used for the frame are characterized to get input data for the model Sound transmission for single frame double walls is studied both experimentally and analytically Paper ID 203 Analytical and experimental study of single frame double wall PAGE 2

3 WAVE APPROACH LINE CONNECTIONS Periodically spaced studs Periodically spaced screws along studs 3-dimensional model (plate/cavity/plate) based on the wave approach for infinite thin plate in flexure Studs modeled as line connection between panels : translational and rotational line springs inducing normal forces and moments to panels Cavity filled with absorbing material modeled as equivalent fluid Lightweight panels Input data for studs : translational and rotational line springs Transition between line connections and point connections when half flexural wavelength of the plates equals the distance between screws Paper ID 203 Analytical and experimental study of single frame double wall PAGE 3

4 SEA APPROACH POINT CONNECTIONS Direct path through cavity is evaluated with wave approach model Flanking transmission path associated to point connections representing screws used to fix panels on studs is evaluated with SEA Point connections modeled as translational spring only Vibrational level difference : D v12 10 log 10 m s2 2 Y 1 Y 2 Y n Real(Y Y t mobility of point connecting tie, for a spring of stiffness K t, Y t =i/ K t Y input mobility of panel n number of connections par unit area damping factor m s density per unit area Flanking path transmission loss : f c critical frequency radiation efficiency TL fl D v12 10 log m c0 f 2 s1 ) c1 t f Paper ID 203 Analytical and experimental study of single frame double wall PAGE 4

5 SEA APPROACH POINT CONNECTIONS Difference between wall studs, boundary studs and boundary rails Boundary rails or Boundary studs: use of mobility for semi-infinite plate excited by a force on the edge Y semiinf inite plate Studs : use of mobility for infinite plate excited by a force Y inf inite plate D m 1 D m s s Boundary rails Boundary studs Other wall Studs Boundary rails : connected to concrete laboratory frame Boundary studs : not connected to concrete laboratory frame Paper ID 203 Analytical and experimental study of single frame double wall PAGE 5

6 Rigid wall EXPERIMANTAL SETUP STUDS CHARACTERIZATION Studs Force Excitation (hammer) Boundary rails Force Excitation (hammer & Rain on the roof) Rigid wall Rigid Floor Rotation effect minimized Measurement of input mobility System size 1.2x0.66 m 2 Deduction of stiffness values in low frequency (before modal behavior) Boundary rails fixed on rigid wall Measurement of vibration level difference System size 2.5x1.2 m 2 Stiffness estimated from 3D SEA model Paper ID 203 Analytical and experimental study of single frame double wall PAGE 6

7 STIFFNESS FOR POINT CONNECTIONS STUDS CHARACTERIZATION Studs Measured K tr-punct (MN/m) Boundary Rails Measured K tr-punct (MN/m) Studs TC Stud TC175 Stud TC Studs AWS Rail C125 Stud AWS Boundary rails C Evaluated stiffness for Rail C175 : 0.17 MN/m Paper ID 203 Analytical and experimental study of single frame double wall PAGE 7

8 TL (db) SOUND REDUCTION INDEX FLANKING PATH Same number of connections for both wall studs and boundary rails Flanking path SEA - Wall Studs - Stiffness 0.2MN/m Flanking path SEA - Boundary rails - Stiffness 0.2MN/m Flanking path SEA - Wall Studs - Stiffness 1MN/m Flanking path SEA - Boundary rails - Stiffness 1MN/m 10 Frequency (Hz) Paper ID 203 Analytical and experimental study of single frame double wall PAGE 8

9 EXAMPLE WALL 1 DESCRIPTION Leaf 1 : GEK13 gypsum board 13 mm thick Leaf 2 : GTS9 gypsum board 9 mm thick Absorbing cavity : 175 mm thick filled with absorbing material (glass wool of =30kg/m 3 and =8 kpa s/m 2 ) Studs : TC175, steel 1.2 mm in thickness, periodically spaced with L=60 cm, screwed every 30 cm Boundary studs : TC175, steel 1.2 mm in thickness, boards screwed every 20 cm Boundary rails : C175, steel 1.2 mm in thickness, boards screwed every 20 cm Tested system of size 4x3 m 2 Transition from line connections to point connections Hz Paper ID 203 Analytical and experimental study of single frame double wall PAGE 9

10 TL (db) EXAMPLE WALL 1 RESULTS Rw in db (C in db) Predicted without stud 55 (-4) Predicted with measured studs characteristics 51 (-3) Measured 52 (-3) Measured Predicted - Without Studs Predicted - CSTB Kmeas Frequency (Hz) Paper ID 203 Analytical and experimental study of single frame double wall PAGE 10

11 EXAMPLE WALL 2 DESCRIPTION Leaf 1 : GEK13 gypsum board 13 mm thick Leaf 2 : GTS9 gypsum board 9 mm thick Absorbing cavity : 125 mm thick filled with absorbing material (glass wool of =30kg/m 3 and =8 kpa s/m 2 ) Studs : TC125, steel 1.2 mm in thickness, periodically spaced with L=60 cm, screwed every 30 cm Boundary studs : TC125, steel 1.2 mm in thickness, boards screwed every 20 cm Boundary rails : C125, steel 1.2 mm in thickness, boards screwed every 20 cm Tested system of size 4x3 m 2 Transition from line connections to point connections Hz Paper ID 203 Analytical and experimental study of single frame double wall PAGE 11

12 TL (db) EXAMPLE WALL 2 RESULTS Rw in db (C in db) Predicted without stud 52 (-6) Predicted with measured studs characteristics 49 (-3) Measured 50 (-2) Measured Predicted - Without Studs Predicted - CSTB Kmeas Frequency (Hz) Paper ID 203 Analytical and experimental study of single frame double wall PAGE 12

13 EXAMPLE WALL 3 DESCRIPTION Leaf 1 & Leaf 2 : GEK13 gypsum board 13 mm thick Absorbing cavity : 125 mm thick filled with absorbing material (glass wool of =17kg/m 3 and =8 kpa s/m 2 ) Studs : ASW mm in thickness, periodically spaced with L=60 cm, screwed every 30 cm Boundary studs : AWS125, steel 1.2 mm in thickness, boards screwed every 20 cm Boundary rails : C125, steel 1.2 mm in thickness, boards screwed every 20 cm Tested system of size 4x3 m 2 Transition from line connections to point connections 150 Hz Paper ID 203 Analytical and experimental study of single frame double wall PAGE 13

14 TL (db) EXAMPLE WALL 3 RESULTS Rw in db (C in db) Predicted without stud 52 (-5) Predicted with measured studs characteristics 48 (-3) Measured 49 (-2) Measured Predicted - Without Studs Predicted - CSTB Kmeas 10 Frequency (Hz) Paper ID 203 Analytical and experimental study of single frame double wall PAGE 14

15 CONCLUSIONS Prediction model, based on wave approach for low frequencies and SEA approach for mid-high frequencies, was presented to evaluate sound transmission through single frame double wall Characterization of studs to get input data for model was implemented Prediction model was validated by comparison with experimental results Prediction model can be used to help industrial partners to improve their products or to develop new products Paper ID 203 Analytical and experimental study of single frame double wall PAGE 15