提出一种新型的复合隔声结构,外部为刚性材料、内部为外接阻尼分流电路的压电PVDF微穿孔板。利用结构的共振吸声作用和压电材料的能量转换作用消耗声能量,进而提高隔声量。为了验证这种复合结构的隔声性能,针对普通无刷直流电机的隔声应用进行实验,实验结果表明电机噪声能量主要分布的频段4~10 k Hz的平均隔声量达到原来噪声的50%。
To measure the performance of high precision air-pressure sensors in below normal pressure,an automatic measurement instrument has been designed and implemented.It can simulate environment of low pressure from 300hPa to 1 000hPa with high accuracy by proportional-integral-derivative(PID)control quickly,and it can also generate various relative humidity by two-pressure control.The results show that this instrument can reach controlled pressure quickly.And it works well with the minimum average pressure difference,and the fluctuation is±0.02hPa at 500hPa.And it can keep in a stable status for a long time.It works well in performance testing of pressure sensors.The structure of the system is simple,takes small investment,and can be operated conveniently.
An ultrasonic energy transference system with a ZnO square piezoelectric thin-film array(SPTFA)structure is presented.The design principle of the system is analyzed,and a device with the SPTFA structure is successfully fabricated based on MEMS processes.The characteristics of the energy transference system are investigated in detail.The experimental results reveal that the resonant frequency of the system is 13 MHz,the maximum voltage of the receiving end reaches 10.87 V when the amplitude of excitation voltage is 10 V,at that time the output power of system is 5.377 mW,and power density is 2.581 mW/cm^(2).The light emitting diode is lit successfully by the system in a distance of 3 mm.
A kind of hybrid device for acoustic noise reduction and vibration energy harvesting based on the silicon microperforated panel(MPP) resonant structure is investigated in the article. The critical parts of the device include MPP and energy harvesting membranes. They are all fabricated by means of silicon micro-electro-mechanical systems(MEMS) technology. The silicon MPP has dense and accurate micro-holes. This noise reduction structure has the advantages of wide band and higher absorption coefficients. The vibration energy harvesting part is formed by square piezoelectric membranes arranged in rows. ZnO material is used as it has a good compatibility with the fabrication process. The MPP, piezoelectric membranes, and metal bracket are assembled into a hybrid device with multifunctions. The device exhibits good performances of acoustic noise absorption and acoustic–electric conversion. Its maximum open circuit voltage achieves69.41 mV.
