Noise reduction and power generation in blower duct using Helmholtz resonator with piezoelectric diaphragm

Abstract

Abstract Ventilation duct systems are indispensable for air purification and room temperature management in industrial and commercial buildings. The noise generated by blowers for ventilating spaces should be as low as possible. In addition, to power the wireless nodes for monitoring the ventilation conditions such as temperature and pressure at any positions in all the ducts, electric power is preferred to be generated in situ without batteries and wired power supply. In this study, to demonstrate simultaneous noise reduction and in situ power generation using a Helmholtz resonator with a piezoelectric diaphragm in a straight circular pipe duct, the frequency properties of the sound pressure level (SPL) with/without the piezoelectric diaphragm and its generated voltage were measured using an in-house apparatus simulating an industrial blower duct. The experimental results show that the Helmholtz resonator with the piezoelectric diaphragm has a noise reduction performance similar to that without the piezoelectric diaphragm. Power generation was improved not only by impedance matching between the inner and outer resistance but also by the frequency resonance between the frequency of pressure fluctuation in the Helmholtz resonator and the natural frequency of the piezoelectric diaphragm. The Helmholtz resonator with the piezoelectric diaphragm achieved a noise reduction of 10 dB from an SPL of 103 dB and power generation of 12 μW at an SPL of 93 dB.