Research On Composite Structure Of Micro-perforated Panel And Noise Control Of Liquid Cavitation Heater

The noise pollution has become one of the most important issues which affect peoples'learning, work and lives. Nowadays the noise prediction and control of products are paid more and more attention to by the society. Micro-perforated panel structure is a new type of absorbing structure, which has been widely used in aircraft noise, car noise, motor noise and construction noise. Statistical energy analysis which is a kind of effective forecast technique of sound and vibration, has successfully applied in aerospace, ships, automobile and so on. In this paper, some research is done about the absorption performance of micro-perforated panel structure. The noise of the liquid cavitation heater is forecasted by statistical energy analysis and controlled by composite sound-insulating structure of micro-perforated panel.Firstly, according to the theory of micro-perforated panel structure, we map out the absorption performance curves of micro-perforated panel structure by simulation. Some research is done about the impact of the four structural parameters on single micro-perforated panel structure from the following three aspects including resonance frequency, maximum absorption coefficient and semi-acoustic bandwidth. Based on single micro-perforated panel structure, we investigated the absorption performance of double micro-perforated panel structure and parallel micro-perforated panel structure.Secondly, we drew some absorption performance curves including single micro-perforated panel structure, double micro-perforated panel structure and parallel micro-perforated panel structure by the results of the standing wave tube experiment. It is consistent with simulation results. Experimental results demonstrate that glass wool can't reflect the high-frequency absorption performance when the cavity of micro-perforated panel structure filled with of glass wool. However when the glass wool is placed in front of micro-perforated panel structure, both the low-frequency absorption performance of micro-perforated panel structure and the high-frequency absorption performance of glass wool can be reflected.Thirdly, we measure and analyze the noise spectrum of liquid cavitation heater and confirm that the cavitation noise is the main noise. Some noise prediction of cavitation reactor are made by statistical energy analysis, we also control the noise of cavitation reactor by improving the structure and applying damping, we also predict noise reduction after control and make a test of noise reduction.Finally, acoustical enclosures are designed in order to control the noise of liquid cavitation heater. It includes appearance design, the design of composite sound-insulating structure of micro-perforated panel, the seal design of cracks and holes and vibration isolation design. We predict its effect by statistical energy analysis and make a test of noise reduction.