Laser Doppler vibrometry measurement of the radiated sound power of a funicular floor system

Abstract

Floor slabs represent a high percentage of the embedded energy in buildings. Lightweight floor systems, such as funicular shell structures, represent an important approach to the reduction of embedded energy in building by reducing material use in a significant way. As the amount of material is reduced, the sound insulation capabilities need to be studied in depth, particularly in the lower frequency range. The high stiffness of the shell structures has been shown with numerical experiments to have great potential for sound insulation in low frequencies. This paper presents laboratory measurements of the radiated sound power an unreinforced concrete funicular floor system in the low frequencies by means of laser Doppler vibrometry (LDV). The presented experiments use the velocities captured by the LDV system, coupled with the Rayleigh integral method to estimate the radiated sound power in an accurate way, without the known mode density problems present in low frequency microphone based measurements. A flat concrete slab of the same mass and dimensions is also tested for comparison. The paper presents the results of the two measurements and outlines guidelines for the acoustic optimization of the funicular floor system.