Helmholtz Resonator for Lead Zirconate Titanate Acoustic Energy Harvester

Acoustic energy harvesters that function in environments where sound pressure is extremely high (∼150 dB), such as in engine rooms of aircrafts, are expected to be capable of powering wireless health monitoring systems. This paper presents the power generation performances of a lead-zirconate-titanate (PZT) acoustic energy harvester with a vibrating PZT diaphragm. The diaphragm had a diameter of 2 mm, consisting of Al(0.1 μm)/PZT(1 μm)/Pt(0.1 μm)/Ti(0.1 μm)/SiO₂(1.5 μm). The harvester generated a power of 1.7×10–13 W under a sound pressure level of 110 dB at the first resonance frequency of 6.28 kHz. It was found that the generated power was increased to 6.8×10–13 W using a sound-collecting Helmholtz resonator cone with the height of 60 mm. The cone provided a Helmholtz resonance at 5.8 kHz, and the generated power increased from 3.4×10–14 W to 1.4×10–13 W at this frequency. The cone was also effective in increasing the bandwidth of the energy harvester