Design of Tunable Acoustic Liner and Adaptive Control System

Traditional acoustic liners used in nacelles and fan ducts include a perforated face sheet bonded to a honeycomb core. A tunable acoustic liner with a piezoelectric substrate is developed to overcome the shortages of current liner such as unchangeable structure and uncontrollable bandwidth. After the piezoelectric panel deformed under the driving voltage, the resonant chamber changed, and the resonant frequency shifts. The finite element method is used to calculate the acoustic system’s resonant frequency and sound pressure distribution. The transmission loss measurement was carried out in an impedance tube to demonstrate the broadband noise control effect of the liner. The experiment result indicates that the TL peak frequency keeps linear with the driving voltage, and the sensitivity is measured to be 0.1 Hz/V. A DC amplified circuit using photo resistor is designed based on constructing the function of driving voltage and noise frequency. Benefit from the adaptive algorithm, when the noise frequency offsets from 756 to 788 Hz, the driving voltage can be automatically regulated from 110 to 420 V, and the liner always keeps resonating. Meanwhile, the sound level was reduced. The adaptive noise control is realized for broadband noise reduction.