Effect of inserting a Helmholtz resonator on sound insulation in a double-leaf partition cavity

Abstract

We investigated the improvement of sound insulation of a double-leaf partition using Helmholtz resonators. We proposed a method of predicting the sound reduction index R 0 at normal incidence using impedance transfer, under the assumption that the resonators installed in the air cavity between the two leaves were independent components of a wall, similarly to boards and studs. Furthermore, for experimentation, a small sample without studs was used to prevent flanking transmission through them. Theoretical and empirical examinations revealed that installing the resonators in the cavity in the following manner was sufficient to control sound insulation at low frequencies. High sound insulation occurred at the resonance frequency f 0 of resonators; the sound insulation decreased at higher and lower frequencies than f 0. The sound insulation at f 0 depended on the acoustic resistance of resonators. When an air layer existed behind the resonators, other peaks and dips appeared at higher frequencies than f 0. Installing both a fibrous absorber and resonators in the cavity was sufficient to recover the decreased performance of sound insulation owing to the installation of resonators.

Acoustic performance of brick masonry walls: Construction defects and influence of installations

“…This combined effects have also been observed by other authors. 21,22 The systems with countless gaps resulted in patterns of insulation that are hard to predict, with greater vulnerability at high frequencies due to smaller wavelengths. Hopkins 7 observed it as a frequent problem in buildings by transmitting sound through porous plates.…”

Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions

“…The latter are usually made of a homogeneous blanket or a multilayer including heavy layers. 2 Much later, Sugie et al 3 proposed a similar heterogeneous material made of fibrous sound absorbers with resonant inclusions in order to improve the low frequency sound transmission loss of double-leaf structures at the mass-air-mass resonance frequency. According to the authors of Ref.…”

“…3, their idea stems from the works of Mason and Fahy, 4 Prydz et al, 5 and Kuntz et al, 6 where the HRs where attached directly on the panel. Sugie et al 3 suggested that including the resonant element within the fibrous sound package in between the two panels allows for a more flexible optimization of the HR effect and a low frequency sound insulation improvement. More recently, the acoustic community had shown a keen interest in this type of resonant structure.…”

Broadband low-frequency sound transmission loss improvement of double walls with Helmholtz resonators

“…[3], layers of so-called membrane-type acoustic metamaterials were placed in between the walls of a double wall partition to achieve considerably improved STL values at the anti-resonance frequencies of the metamaterials. By adding Helmholtz resonators to the cavity of a double wall, significant STL enhancement can also be achieved 25 around the resonance frequencies of the embedded resonators [4][5][6]. This particular concept has been studied extensively and it has even been tested successfully inside the sidewall of a real aircraft structure [7].…”