On the acoustic radiation efficiency of local resonance based stop band materials

The application of materials with stop bands is emerging as a novel way of creating meta-materials with good vibrational behaviour. The acoustic radiation efficiency in these stop band zones is often not investigated. This paper formulates an uncoupled vibro-acoustic unit cell model of a plate with local resonant stop band behaviour, based on the addition of a grid of tuned resonators. The results are compared with a vibro-acoustic coupled model for a finite equivalent of the infinite structure. It is shown that the beneficial vibration reduction that is achieved in a stop band can be acoustically reduced or enhanced by the change in radiation efficiency of the structure. When care is taken in the design of the stop band, a stop band material with good vibro-acoustic behaviour can be achieved.