Divriği Hospital - Medieval Healing Venue and Its Acoustic Characteristics

Divriği Great Mosque and Hospital as one of the World heritage monuments on UNESCO’s list was the subject of research. More precisely, the focus was on the architecture and the acoustic characteristics of the hospital built in 1228/1229 by Mengüjeck dynasty, a branch of Anatolian Seljuks. For the analysis purposes, a 3D model of the hospital was created, and the acoustic simulation was conducted. The results of the acoustic analysis show that the architectural characteristics of the hospital fulfill the acoustic standards for the good reception of the sound for the audience, and that it can be concluded that Divriği hospital venue supports the hypothesis of being suitable for the healing purposes. Hospital was designed to support the sound realization and to support the environmental soundscape in conjunction with the sounding makams, which supports the music therapy healing effect. It can be concluded that music therapy had acoustical support in the construction of Anatolian Seljuk hospitals, which have characteristics of concert halls and were built as acoustic (music) venues.

Acoustic Simulation of the Electric Vehicle Motor

People pay more and more attention to NVH (N-noise, V-vibration, and H-harshness) characteristics of electric vehicles and motors. The vibration and noise of the electric vehicle motor is a complex multi physical field problem, related to electromagnetic, mechanical, structural and sound fields. In this paper, firstly, the Maxwell electromagnetic field analysis software is used to build the electromagnetic simulation model of PMSM(Permanent magnet synchronous motor) motor, and then the electromagnetic excitation is calculated. Then, the magnetic solid coupling analysis is carried out by using the Maxwell module and harmonic response module of ANSYS Workbench, and the harmonic response of the motor structure under the action of electromagnetic excitation is simulated. After the simulation of magnetic solid coupling is completed, the BEM(Boundary element method) simulation of the permanent magnet synchronous motor is carried out with the acoustic simulation software LMS Virtual Lab. The acoustic simulation of the permanent magnet synchronous motor shows that the sound pressure level at three measurement points have obvious peak value at 3700Hz, 4500Hz, 5400Hz and 6400Hz respectively. The acoustic simulation results lay the foundation for the vibration and noise reduction of the motor.

Detection, Integration, and Optimization of Acoustic Field Simulation in the Closed Space

Noise pollution in the closed space such as railway carriage is an important problem because the noise pollution seriously affects comfort and health of people in the closed space. We propose the method to detection, integration, and optimization of acoustic field simulation in the closed space. First, we analyze the acoustic field distribution in the virtual 3D close space. We use harmonic sound wave propagation in the closed space and present the distribution according to geometric analysis. Second, we introduce Delaunay triangulation and k-means clustering into visualization to form the quiet zone and show it in 3D perspective. Our method used acoustic simulation to develop the sound barrier system. The simulation results show that our method can improve the analysis of the noise problem in the closed space.

An explicit time-domain FEM for acoustic simulation in rooms with frequency-dependent impedance boundary: Comparison of performance in 2D simulation with frequency-domain FEM

Accurate boundary modelings that address the frequency-dependent sound absorption characteristics of various sound absorbers are crucial for wave-based room acoustic simulation. In time-domain simulations, however, a computationally demanding convolution appears in frequency-dependent impedance boundary conditions. The present paper proposes a room acoustic solver with a fourth-order accurate explicit TD-FEM, incorporating a frequency-dependent absorbing boundary condition efficiently using a recursive convolution method, namely the auxiliary differential equation (ADE) method. Its performance against the fourth-order accurate frequency-domain FEM is examined via 2D real-scale room acoustic problems, solving a sound propagation in an office room up to 4.5 kHz. Firstly, we describe briefly the formulation of the proposed room acoustics solver based on the explicit TD-FEM. Then, the discretization error property of the proposed method is evaluated via an impedance tube problem, including a frequency-dependent impedance boundary of porous sound absorber. Finally, the accuracy and efficiency of the proposed method are demonstrated with the comparison of frequency-domain FEM solver, which uses a sparse direct solver for the solution of the linear system at each frequency. Results showed the proposed method can perform an acoustic simulation with significantly low computational costs compared to the frequency-domain solver while keeping an acceptable level of accuracy.

Implementation of Direct Acoustic Simulation using ANSYS Fluent

Direct Acoustic Simulation (DAS) is a powerful Computational Aero Acoustics method that obtains hydrodynamic and acoustic solutions simultaneously by solving compressible Navier-Stokes equation together with state equation of ideal gas. Thus, DAS has advantages for cases with flow acoustic coupling and high Mach numbers (). With an increasing demand of massive-scale calculations, a robust numerical solver for DAS is required. ANSYS Fluent is a suitable CFD platform with proven robustness. However, there is no direct implementation of DAS in the current version of ANSYS Fluent. The present study, therefore, aims to investigate an approach for implementing DAS using ANSYS Fluent. Given the acoustic part of fluctuations is much smaller than the hydrodynamic part in amplitude, a DAS solver requires high accuracy and low dissipation. Based on these needs, proper solution methods, spatial discrete methods and boundary conditions are firstly determined through simple calculations of two dimensional propagating plane waves. Afterwards aeroacoustics of a two-dimensional cavity flow at 0.6 is calculated to verify the capability for solving separating flow with the aforementioned set-up. Finally, aeroacoustics of a cylindrical bluff body at a turbulent regime and 0.2 is calculated in three-dimensions to verify the capability for solving turbulent flow using Monotonically Integrated Large Eddy Simulation.

Visualization of bat “echo space” using acoustic simulation

Behavioral experiments with acoustic measurements have revealed the intriguing strategies of flight navigation and the use of ultrasound by echolocating bats in various environments. However, the echolocation behavior of bats has not been thoroughly investigated in regard to the environment they perceive via echolocation because it is technically difficult to measure all the echoes that reach the bats during flight, even with the conventional telemetry microphones currently in use. Therefore, we attempted to reproduce the echoes of bats during flight by combining acoustic simulation and behavioral experiments with acoustic measurements. As a result, we visualized the spatiotemporal changes in the echo incidence points detected by bats during flight, which enabled us to investigate the “echo space” revealed through echolocation. In addition, we could observe how the distribution of visualized echoes concentrated at the obstacle edges after the bats became more familiar with their environment. Furthermore, our results indicate that the direction of preceding echoes affects the turn rates of the bat's flight path, revealing their original echolocation behavior.