Optimization of resonator length and loudspeaker’s housing length of an acoustic energy harvester

An acoustic energy harvester (AEH) is an energy conversion device that converts sound energy into electricity. The purpose of this device is to harvest unused environmental noise into something useful. The typical components of the AEH are an acoustic resonator and an acoustic transducer equipped by its housing. In this research, a 4-in commercial woofer loudspeaker was used as the acoustic transducer. The loudspeaker was installed on a cylindrical housing which was made of a 5-in. PVC (polyvinyl chloride) pipe with an inner diameter of 13.4 cm. The acoustic resonator was built of 4-in. PVC pipes. The objective of this research is to optimize the combination of resonator length and housing length to obtain the highest electricity power. The experiment was done by using 100 dB SPL of sound waves at various frequencies. The electric power was measured on a 4.6-ohm load resistor for several variations of resonator length and loudspeaker’s housing length. The experimental results showed that the optimum resonator length and housing length were 136 cm and 16 cm, respectively, which produced the highest rms (root-mean-square) electric power of around 140 mW.