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02.02 Inverse Approaches in Vibro-Acoustics

Traveling-wave control of the bending wave in a beam for high quality sound radiation
Time: 6:20:00 AM

Author: Ki-Ho Lee

Abstract ID: 1696

The bending wave generated by the actuator exciting a panel can be controlled to be in the traveling wave form void the structural resonances, which deteriorates the radiated sound if the panel is used as a speaker. Although such traveling-wave control method (TCM) yields a wider effective frequency range than the modal control method, the requirement of using many actuators is the practical problem yet. If a beam is employed instead of a plate as a panel speaker, the number of actuators can be reduced despite a smaller radiating surface than a plate. This study adopts three actuators for the beam control using TCM. An actuator excites the beam in the middle position, and the two actuators near the two edges are used to suppress the reflected waves from the boundaries. The control result shows that the driving-point mobility of the primary actuator is converted into that of an infinite beam, which means that the boundaries are changed into anechoic ones and the structural resonances are eliminated. Accordingly, the beam radiates a smooth sound spectrum without sharp peaks and troughs related to the resonant responses. Effects of material and dimension in determining the effective frequency range are also explored.

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Vehicle interior noise and vibration prediction by combination analyses of Component and Operational TPA
Time: 7:00:00 AM

Author: Takuma Tanioka

Abstract ID: 1966

In this study, we propose an analytical method consisting of Operational TPA (OTPA) and Component TPA (CTPA) to predict the vehicle interior noise and vibration without the vehicle operational test in case the noise source such as engine was modified. In the proposed method, the blocked force of the noise source was obtained at a test bench and the vibration at the source attachment point on the vehicle was calculated by CTPA. After then, the response point signal (interior noise / vibration) is estimated from several reference point signals including the calculated vibration by OTPA. For the verification of this method, a simple vehicle model which is composed of four tires and a motor was prepared in addition to a test bench. OTPA was firstly applied to the vehicle model to analyze the contribution from tires and a motor to the body vibration (response point). The blocked force of a modified motor was obtained by CTPA at the test bench and the force was used to predict the response point by OTPA. Finally, the estimated interior vibration was compared with the actual measured response point vibration when the motor was replaced on the vehicle model and the accuracy was verified.

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Computation analysis of regularization methods and parameter selection for acoustic source radiation modes reconstruction of vibrating plates
Time: 6:40:00 AM

Author: Luis Corral

Abstract ID: 2655

Source localization and power estimation is a topic of great interest in acoustics and vibration. Acoustic source radiation modes reconstruction is a method of particular interest. Solutions leads to determinate sound/vibration power and surface velocity distribution from sparse acoustics samples. It has been shown that the quality of the results depends on Tikhonov regularization parameter. This inverse method is based on the radiation resistance matrix and we show that a single instruction multiple threads computing approach for graphics processing unit device exhibit better speed performance than common approaches to achieve the solution. We compare four regularization and three estimating methods for regularization parameters. We use a similarity measure to the simulated cases in three frequencies. Tikhonov regularization exhibits best reconstruction results. However, truncated singular vector decomposition also shows good performance with the advantage of not using a regularization parameter. Graphics processing unit implementation reduce reconstruction's computing time at least in a half.

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Shaping acoustic radiation induced by vibrotactile rendering on a touch surface
Time: 12:40 pm

Author: Sangwon Park

Abstract ID: 2661

Many electronic devices with touch-sensitive surfaces aim to provide vibrotactile feedback, along with visual or auditory feedback, to facilitate the interaction between the user and the interface. In parallel to these efforts, recent studies developed various vibration rendering techniques, enabling more complex vibration patterns to be generated on the touch surface. However, few have addressed sound radiation induced by vibrotactile rendering on a touch surface, which could significantly impact the haptic interaction's overall perception. This study presents a method to shape the acoustic radiation due to rendering high-fidelity vibrotactile feedback on a touch surface. The proposed method utilizes measured frequency response functions and a vibroacoustic representation of the touch surface to define the relationship between actuator driving signals, vibration responses on the touch surface, and radiated sound power. Proper actuator driving signals are derived from the optimization problem formulated using the relationship. The proposed method was demonstrated through vibration rendering experiments on a touch surface comprising an acrylic plate and voice coil actuators. The results showed that the proposed method could shape the acoustic radiation while rendering target vibration patterns at desired positions on the touch surface. This study's proposed method could allow haptic engineers to design vibrotactile feedback and sound radiation simultaneously for a more compelling haptic experience.

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