Comparison between Resonance and Non-Resonance Type Piezoelectric Acoustic Absorbers

Abstract

In this study, piezoelectric acoustic absorbers employing two receivers and one transmitter with a feedback controller were evaluated. Based on the target and resonance frequencies of the system, resonance and non-resonance models were designed and fabricated. With a lateral size less than half the wavelength, the model had stacked structures of lossy acoustic windows, polyvinylidene difluoride, and lead zirconate titanate-5A. The structures of both models were identical, except that the resonance model had steel backing material to adjust the center frequency. Both models were analyzed in the frequency and time domains, and the effectiveness of the absorbers was compared at the target and off-target frequencies. Both models were fabricated and acoustically and electrically characterized. Their reflection reduction ratios were evaluated in the quasi-continuous-wave and time-transient modes.Sensors 2020, 20, 47 2 of 17 previous studies. However, it is difficult to compare them due to the different approaches involved. Therefore, we believe that only resonance and non-resonance models with similar structures should be compared. In this study, resonance and non-resonance models suitable for the target frequency were designed via mathematical analysis. Based on the designs, the resonance and non-resonance models were fabricated and evaluated. The absorber was configured in the form of tiles, and the lateral size of the structure was equal to half of the wavelength. Our proposed resonance and non-resonance models were fabricated by stacking commercially available lead zirconate titanate (PZT). Various studies have previously investigated the stacking or direct fabrication of devices [14-19]. Materials and Methods ConceptIn the case of a piezoelectric material, vibration along the thickness direction is observed when an electrode is applied, and the sound spreads around both the front and rear sides of the piezoelectric material. The resonance frequency range of a piezoelectric material depends on its thickness. The thickness of a piezoelectric material and its resonance frequency are inversely proportional, i.e., the thinner the piezoelectric material, the higher is its resonance frequency and vice versa.In this paper, we present a model that resonates in the low frequency region of the target frequency and a non-resonance model that deviates from the target frequency. The proposed resonance and non-resonance models incorporated a function that cancelled a certain portion of the incident sound waves.The incident and reflected waves must be separated to cancel the incident sound wave. Two receiving sensors were required to separate the incident and reflected waves, as the signals were measured based on the overlap between these two waves. The incident (P + ) and reflected (P -) acoustic pressures were the input and output of the system, respectively (Figure 1). We calculated the incident and reflected acoustic sensitivities based on the different receiving sensitivities of the two sensors obtained using the Krimholtz-L...

Design and Analysis of an Active Reflection Controller That Can Reduce Acoustic Signal Refer to the Angle of Incidence

“…The compensation signal can be calculated by measuring the two receiving sensors per unit. These compensation methods were presented in our previous work [ 42 ] concerning normal incidence waves. However, in the case of a non-normal angle of incidence, the transmitted acoustic signal is omnidirectional, and hence generates undesired acoustic signals in various directions.…”

“…To understand the electrical characteristics and output pressure of a transducer at the design stage, we analyzed it based on an analytical model. As shown in Figure 2 , the model used for the analysis consisted of one layer of transmitter, two layers of receiving sensors, and three layers of acoustic windows [ 42 ].…”

“… is the area of the transducer, and d is the thickness of the transducer to be analyzed. is the coupling constant, and is the resonance frequency of the transducer [ 36 , 42 ]. …”

“…A method that can reduce the acoustic signal according to the angle of incidence in water was derived by conducting an experiment. In our previous study [ 41 , 42 ], a study on normal incidence was performed, so we focused the study on the angle of incidence, except for normal incidence. The controller we have presented can be applied to an underwater vehicle when configured as an array.…”

Application of Adaptive Wave Cancellation Underwater to a Piezoelectric-Material-Based Multilayer Sensor

“…In this study, the properties of each material, such as the Q factor (quality factor), thickness, and acoustic impedance, were based on the properties obtained from the experimental values. The transmitting/receiving sensitivity in the simulation was calculated using the equivalent circuit model equation [19][20][21][22]. Experiments for measuring both sensitivities were conducted in a water tank that was 1 m long, 0.75 m wide, and 0.5 m high ( Figure 5).…”