The Effect of Suspension Systems on the Sound Insulation of Suspended Ceilings

I-INCE is supported in part by sustaining members like AMC Mecanocaucho. AMC designs and produces anti-vibration mounts as well as noise insulation composites for industrial and building sectors. Their noise and vibration solutions combine rubber, metal, springs, Sylomer® and other materials. AMC has provided noise and vibration control products since 1969.  

AMC recently collaborated with the AINS Group in Finland to measure and simulate the sound insulation characteristics of suspended ceilings. Aitor Lopetegi of AMC summarizes the work here. You can download a longer version of their work from ASA’s POMA archives here:  Link 

Introduction to Suspended Ceilings 

Suspended ceilings are commonly used to improve sound insulation between overlapping spaces, particularly in room-within-a-room applications. The typical setup includes: 

  • Layers of building boards (often plasterboards or wood-based boards). 
  • A frame behind the boards for installation, usually made of metal or timber. 
  • A suspension system, either elastic or rigid hangers, attaching the ceiling to the floor above, creating an airspace in between. 

The system forms a mass-spring-mass system, where the airspace serves as a spring and the boards function as masses. This structure helps in reducing sound transmission through both airborne and impact noise.

Acoustic hangers suspending an acoustic ceiling

Suspension Systems Compared 

Two types of suspension systems were analyzed: 

  • Rigid hangers (system F1) 
  • Elastic hangers (system F2), specifically elastomeric hangers from AMC Mecanocaucho. 

The elastic suspension system showed significant improvement in both airborne and impact sound insulation compared to the rigid hangers, particularly at frequencies above 100 Hz. This is due to the reduced mechanical coupling between the ceiling and the floor when using elastic hangers.

Measured sound reduction index (left) and impact sound pressure levels (right)

Materials and Methods 

The study analyzed sound insulation performance using finite element method (FEM) simulations, focusing on two suspended plasterboard ceilings below a concrete slab. In both configurations (F1 and F2): 

  • The plasterboards were 13 mm thick, hung below a 140 mm concrete slab. 
  • The air gap between the slab and the plasterboard was 130 mm, including 100 mm of mineral wool for additional sound absorption. 

Key Findings 

Laboratory measurements confirmed that using elastic hangers greatly improves sound insulation. The results showed: 

  • An increase in the weighted sound reduction index (∆R_w) and a significant reduction in impact sound pressure level (∆L_n,w) when elastic hangers were used (system F2) compared to rigid ones (system F1). 

The simulations also confirmed that elastic suspension systems provide better low-frequency sound insulation than rigid systems, improving performance below 100 Hz. 

Simulation Techniques 

Finite element simulations were performed using COMSOL Multiphysics to evaluate the sound reduction index (R) and normalized impact sound pressure level (Ln) across a range of frequencies (50-5000 Hz). These simulations were supported by parametric calculation models developed by AINS Group. 

The spring-damper model was used to simulate the hangers, and it accurately replicated the behavior of the elastomer hangers. It allowed for the evaluation of the resonance frequencies of the mass-spring-mass system, which occurred around 11.5 Hz for elastic hangers. 

Results 

  • Airborne sound insulation: Elastic hangers showed a 7 dB improvement in the sound reduction index (R_w) compared to rigid hangers. 
  • Impact sound insulation: The improvement was even more significant for impact sound, with a 15 dB reduction in the impact sound pressure level (L_n,w).
Simulated sound reduction index (left) and impact sound pressure levels (right)

Conclusion 

The study demonstrates that elastic suspension systems provide superior sound insulation performance compared to rigid hangers. The use of elastomeric hangers results in better decoupling of mechanical vibrations between the ceiling and the floor, leading to improved performance, especially in the critical frequency ranges. 

Summary of Benefits of Elastic Hangers: 

  • Improved airborne sound insulation, especially above 100 Hz. 
  • Superior impact sound insulation, with marked improvements in low-frequency performance. 
  • Effective in decoupling vibrations, reducing mechanical transmission through the building structure.