Vibro-Acoustic Energy Transmission Analysis of the Acoustic Cavity with Multiple Partial Partitions

The general dynamic characteristics of the acoustic cavity with multiple partial partitions are presented in this thesis. A theoretical model has been developed for predictions, and several configurations are analyzed. To describe the apertures on the interface of subcavities, the virtual air panel assumption is introduced into the improved Fourier series system. The governing equations of the coupling system are derived by using the energy principle. The results obtained with the proposed model are firstly compared with the numerical calculations based on the finite element method (FEM). Subsequently, a configuration made up from a rigid cavity partitioned by a partial steel panel has been specifically built, and the forced responses of the coupling system have been measured for comparison and model validation. The present results are excellent over most of the studied frequency range. Furthermore, the visualizations of the interior sound intensity field of the acoustic cavity with three partial partitions under different frequencies are researched to illustrate the energy transmission paths and vibro-acoustic coupling mechanism of the complicated system. The obtained results are believed to be helpful in the optimal design of the vibro-acoustic coupling system with optimal sound insulation capacity.

Structure-Acoustic Coupling Analysis of Vibration and Underwater Acoustic Radiation of a Ring-Stiffened Conical Shell

The underwater acoustic radiation of the submarine power cabin has recently become a hot topic in the industry and also in the academia. In this article, the vibration and underwater acoustic radiation of a ring-stiffened conical shell with bases are investigated numerically by means of the combination of the finite element method and boundary element method. The acoustic radiation field is obtained by the traditional acoustic field model and ISO acoustic field model, respectively. A series of numerical examples are given, and the results are compared. Besides, the sound pressure at different positions with frequency is further studied. It is shown that the sound radiated by the structure mainly propagates to the side directions of the shell and propagates relatively less to the front side and the rear side.

Effect of modeling sidewalls on tire vibration and noise

Low-noise tire design demands the potent model, which regards accessible parameters in the design process before manufacturing a tire. Unlike most previous analytical models that integrated tire treadband with sidewalls with an assumption of identical properties, this research segregates them. The separation clarifies the effects of each tire part on vibration and noise individually, which has not been presented in previous publications and is noteworthy in design. The model is developed considering three connected plates, describing treadband and sidewalls, on an elastic foundation derived from vibro-acoustic coupling inside the tire. Natural frequencies are determined by the Galerkin method using modes shapes satisfying all boundary conditions. The vibration response of a tire rolling on the road is then formulated utilizing Green’s function and convolution integral. Eventually, vibrational tire noise is calculated by the boundary element method. Comparing the proposed model with the repeatedly used integrated plate model has indicated the dissimilarity of treadband and sidewall responses with a difference of 1.4 dB(A) in total noise level. Moreover, implemented parametric study based on a small central composite design has revealed their parameters’ distinct influences on generated noise. For instance, increment in treadband thickness reduces sound level, while decreasing sidewall thickness effectively leads to noise reduction. So, the proposed model is worth employing instead of the previous overused integrated model to predict and reduce tire noise.

Audible acoustics from low-magnitude fluid-induced earthquakes in Finland

Earthquakes are frequently accompanied by public reports of audible low-frequency noises. In 2018, public reports of booms or thunder-like noises were linked to induced earthquakes during an Engineered Geothermal System project in the Helsinki Metropolitan area. In response, two microphone arrays were deployed to record and study these acoustic signals while stimulation at the drill site continued. During the 11 day deployment, we find 39 earthquakes accompanied by possible atmospheric acoustic signals. Moment magnitudes of these events ranged from $$-0.07$$ - 0.07 to 1.87 with located depths of 4.8–6.5 km. Analysis of the largest event revealed a broadband frequency content, including in the audible range, and high apparent velocities across the arrays. We conclude that the audible noises were generated by local ground reverberation during the arrival of seismic body waves. The inclusion of acoustic monitoring at future geothermal development projects will be beneficial for studying seismic-to-acoustic coupling during sequences of induced earthquakes.