Transmission loss optimization using genetic algorithm in Helmholtz resonator under space constraints

The development of high-performance mufflers associated to a compact volume it is of great importance in industrial field in order to obtain duct noise reduction in an economically and efficiently way. The Helmholtz resonator (HR), a classical reactive muffler, is considered in this work. The main purpose of this paper is to optimize numerically the sound transmission loss (TL) of the HR, since TL is an intrinsic characteristic of the muffler and does not depend on the source or termination impedances. The optimization methodology consists in maximizing the TL obtained for a pure tone frequency under dimensional constraints when the HR is considered mounted in a duct system. In order to search for the optimal dimensions of the HR cavity, an evolutionary search algorithm has been used. The sound pressure data is obtained from a finite element (FE) model (Ansys) of the system HR/duct which communicates with the genetic algorithm (GA) implemented in Matlab software. Many numeric simulations were performed varying GA parameters: number of generations and population size. The results show a strong match dependency between these parameters as well the importance of the bounds constraints range. Optimized HR has a gain of approximately 35 db attenuation in the frequency of interest when compared with the baseline.