Abstract
This paper deals with an alternative modal active control approach to reduce sound transmission through a structure excited by an acoustic wave. Active control makes it possible to conserve lightness while improving acoustic performances. “Modal mass damping control” is proposed for light and small structures having slight modal overlap. The aim of this control is to modify the modal distribution of high radiation efficiency modes with active modal virtual mass and active modal damping. The active virtual mass effects lower eigen frequencies to less audible frequency range while reducing vibration amplitudes in a broad frequency range. An application of this concept is presented in a simple smart structure. It is harmonically excited on large bandwidth by a normal acoustic plane wave. Results obtained by active modal virtual mass and damping control are compared to other modal control approaches.
Highlights
The acoustic transmission loss can be improved by passive methods such as mass addition (Mass Law [1]), double panel, and/or the use of sound absorbing materials
In the 1930s, research focused on active noise control ANC (Lueg’s Patent [2]) in which a secondary field destructively interferes with the primary disturbance
A new modal active control is proposed in this paper
Summary
The acoustic transmission loss can be improved by passive methods such as mass addition (Mass Law [1]), double panel, and/or the use of sound absorbing materials Most of these techniques generally involve an increase in mass or volume to provide a good insulation at low frequencies. When structures are relatively small and light, the panels have low modal overlap, so in this case, modal control appears to be adapted It enables limiting the number of active components and concentrating control energy on high radiation efficiency modes. Active modal damping squeezes sound power peaks and controls low radiation efficiency modes which may be excited and transfer vibrating energy to structure bounds. It is compared to other vibroacoustic modal controls in simulations
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