High-sound-insulation double floor structure with Helmholtz resonators: Experimental study on effect of resonator specifications

Abstract

We have developed a high-sound-insulation double floor structure using Helmholtz resonators. The main targets of this structure are a lot of old apartment buildings that should be renovated, which have thin slabs and cannot sufficiently insulate floor impact sound. The proposed double floor structure greatly improved the insulation performance for heavy-weight floor impact sound in a real old apartment building with 110-mm slab: about 10 dB for 63-Hz and 125-Hz octave bands. In this presentation, experimental results are shown using a small unit structure partially taken out from the whole double floor structure to thoroughly grasp the actual vibration phenomenon. The results are compared to calculation results obtained from a two-particle system theory. Main conclusions are summarized as follows: (i) A sufficiently large rigidity of the resonator walls and a large number of resonator necks are required for obtaining a clear dip in the vibration transmissibility as calculated from the two-particle system theory. (ii) The horizontal and vertical displacement of the resonator necks hardly affects the vibration transmissibility. (iii) The effects of other factors such as the neck length and neck number are qualitatively predictable by the two-particle system theory.