Acoustic transmission line based modelling of microscaled channels and enclosures

Abstract

An analytical model is presented that describes the acoustical impedance of cylindrical tubes and concentrically connected systems of such tubes valid up to the ultrasonic application. This allows the evaluation of microsized geometries encountered in acoustical microdevices, such as housing enclosures and sound port Helmholtz resonators. Each tube is treated as an acoustic transmission line (TL). Connected tubes are described using a coupling impedance, which accounts for viscous and inertial effects due to duct size changes. The acoustic TL model is directly derived from Navier-Stokes and energy equation, including frequency dependent boundary layer effects of the viscous and thermal dissipation. The results for various evaluated enclosure and resonator geometries are in good agreement with finite element method (FEM) simulation in both audio and ultrasonic frequency range and are compared to dedicated lumped element models referenced in literature. The presented model provides benefits in three ways: it is faster than FEM simulation and allows an implementation into analytical models and circuit simulation tools. Finally, it allows geometries with characteristic dimensions close to and above the wavelength to be treated with high precision in contrast to lumped element models.

Locating Nidi for High-Frequency Chest Wall Oscillation Smart Therapy via Acoustic Imaging of Lung Airways as a Spatial Network

“…8. The majority of earlier studies [13], [21], [26]- [29] focus on the changeable physical frequency features and no geographical information was correlated with nodes in the airway. Thus, the airway network in this study was converted into a spatial network by integrating the spatial position (x, y) to each node, which can produce the acoustic image for lung function assessment as shown in Fig.…”

“…3(a). The air pressure and airflow rate are comparable to electrical potential and current, respectively, when the respiratory airways are analyzed as an electrical network [13], [21], [26]- [29]. The kth layer's impedance and admittance can be presented in ( 5), ( , ) , 0, .…”

“…Most of the previous works investigate the variable physical frequency characteristics [13], [21], [26]- [29], and no spatial information is associated with the nodes. In this study, the spatial location (x, y) was integrated to each node to transform the airway network into a spatial network and generate the resulting acoustic image.…”

“…In this study, the spatial location (x, y) was integrated to each node to transform the airway network into a spatial network and generate the resulting acoustic image. The acoustic image can be initiated once the node voltage Vn, which is analogous to the acoustic pressure Pn distribution within the airways [13], [21], [26]- [29] is obtained. The sound pressure in dB within the airways is computed as,…”

Theoretical model and dynamic wave-amplification effect of the high intensity Helmholtz sound source

“…The two components and the air medium within them constitute an acoustic vibration system, of which operation agrees with the non-linear regime (Vargas et al, 2018). Combing with the lumped parameter principle and the sub-wavelength size of the components (Anzinger et al, 2019; El Bouzidi et al, 2019; Long et al, 2018), the vibration system can equal to an impedance analog system. The previous work mainly contains the micro (Han et al, 2018; Kaina et al, 2015) and macro (Wu et al, 2019) integration of HR array (Fang et al, 2006; Maurel et al, 2018), the performance exploration of single HR with different size and geometry (Li et al, 2017), and the feedback control (Mao et al, 2018).…”