Application Cases

Experiment Name: Application of Voltage Amplifiers in the Reconstruction of Cross-Sectional Gradient Fields of Acoustic Waves and Their Utilization in Acoustic Wave Field Processing

Experimental Content:
Underwater acoustic signals cause changes in the refractive index of the medium during propagation. When a laser passes through an acoustically disturbed medium, the spatial variation in the refractive index induces deflection of the laser beam. A position-sensitive detector (PSD) is used to sense this deflection. The deflection of the laser beam can be divided into two components: one within the plane traversed by the laser beam, and the other perpendicular to that plane. By combining tomographic results from both deflection components, the gradient field of the propagating acoustic wave on the cross-section can be obtained. This represents an extended version of beam deflection tomography. Based on the wave field gradient and relative sound pressure distribution, the Kirchhoff integral theorem can be directly applied for further calculation and analysis of the wave field.

Research Direction: Acousto-Optic Sensing, Sound Field Reconstruction

Testing Equipment: ATA-4051 High-Voltage Power Amplifier

Experimental Procedure:
The experimental setup is shown in the figure. A water tank is filled with water, and acoustic absorbers are placed at the bottom. The acoustic wave field is generated by a transducer. A signal generator produces an 180 kHz signal, which is amplified by the Aigtek ATA-4051 high-voltage power amplifier before being applied to the transducer to generate acoustic signals. The laser beam emitted from the laser source undergoes deflection as it passes through the water surface modulated by the acoustic wave. A PSD is placed on the opposite side of the tank to receive the outgoing beam. The displacement of the light spot reflects the integral of the sound pressure gradient along the laser beam path.

The transducer is mounted on a platform that can move perpendicular to the laser beam direction, enabling scanning along parallel lines. After completing one scan, the transducer is rotated to another angle, and the scanning process is repeated until a 180° angular range is covered. The signal generated by the transducer is synchronized with the data acquisition system for reconstructing the instantaneous acoustic field.

Experimental Results:
Using the data obtained from the experiment, we constructed two representations of the acoustic wave field: one showing the relative distribution of sound pressure, and the other depicting the three-dimensional gradient of the acoustic wave field cross-section. The first row in Figure 1 displays the relative pressure distribution of the acoustic wave field (see Video 1). To clearly illustrate the gradients within the field, we show the x and y components of the gradient in the second row and the z component in the last row (see Video 2).

To validate the accuracy of the reconstruction results, we compared them with simulation results obtained using the same parameters. Since the pressure distribution on the cross-section shares the same structural characteristics as the gradient field components in the x and y directions, we only present the comparison results for the pressure distribution and the z component. As shown in Figure 2, the waveform patterns are very similar at each sampling time.

Figure: ATA-4051C High-Voltage Power Amplifier Specifications and Parameters