In the Tuning Fork - Part 1 and Tuning Fork - Part 2 we set up and solved an Elmer study for the modes of vibration of a tuning fork. We learned that the principal mode of the fork, the one related to the nominal frequency of the fork, is very marginally affected by boundary conditions affecting the handle of the fork. In this episode we will attempt studying the acoustic field emitted by the fork in the surrounding air. In other words, we will start exploring the coupling of vibration and acoustics.

In the Tuning Fork - Part 1 episode we setup a new study for the determination of the elastic modes of vibration of a tuning fork. Our study made use a few meshing and solver setting ideas we learned along the way, including the use of $p$-elements. In this episode we will examine the results from the Elmer simulation.

The very first episode in which we introduced Elmer was the Elastic Modes of a Metal Bar episode. In that episode we introduced Elmer by solving a linear elasticity eigenproblem, and mentioned how vibration is an integral part of acoustics, being vibrating bodies one of the principal causes of airborne sound radiation. In this new series of episode we will explore vibration further, integrating in it what we learned so far, and we will explore vibro-acoustic coupling with Elmer.

This project has now quite a few articles and simulations going. Unfortunately, the way the Julia code repositories were set up is not very functional and is not scaling well to many repositories. For this reason, this site will undergo a period of refactoring. The Status Quo At the moment there are few additional Julia code repositories that contain helper code, mainly for postprocessing and to create the plots in this website.

In the Home Studio - Part 3 and Home Studio - Part 4 episodes we referred to the results of our frequency sweep as frequency responses. In those episodes we calculated the steady state pressure disturbance in a room at different frequencies and sampled the field at a couple of locations so to be able to plot the steady state magnitude at those locations as a function of frequency. It is intuitive to refer to this result as a frequency response, in the sense that the field magnitude as a function of frequency gives us an understanding of how strong the steady state disturbance is at any given frequency in our study.

In the Home Studio - Part 3 episode we simulated the steady state pressure field for a realistically shaped room governed by the linear wave equation. The boundary condition for the room was that of ideally rigid walls. We seen that the effect of such a boundary condition is an extremely uneven frequency response. This due to how sharp the resonances of the room are. In this episode we will introduce slightly more realistic boundary conditions and see what the effect on the solution is.

In the Home Studio - Part 1 episode we gave a first look at the response of a realistically shaped room with rigid walls. We understood how to develop and run a model with an uniform velocity sphere source placed somewhere in the room. We run the model up to $400$ $\text{Hz}$ with the help of the convergence considerations outlined in the Dealing with Convergence Issues episode. In the Home Studio - Part 2 episode instead we used Elmer’s WaveSolver to compute the eigenmodes of the room.

In the previous episodes we manipulated some of the result fields from Elmer with meshio, a very nice Python package that allows us to do many useful operations with meshes and fields. However, in the episodes we did not focus into the details of how to use the package. Whilst this webiste is perhaps not the best place to do so, as the best place to understand how to use a package is, of course, its official documentation, it is useful to collect here few examples and remarks about using it with Julia, the programming language we are using for this project.

In the Home Studio - Part 1 episode we computed the steady state field of a realistic, but still rigid walled, room. We put a source in the room, modelled as a flux boundary condition, and run the study at few different frequencies. The solutions that we found were reminiscent of modal patterns, which is expected as the low frequency response of a room is dominated by its resonances. However, that kind of study does not inform us on the actual resonance frequencies of the room, which are properties of great interest, as well as how the associated modal shapes (eigenmodes, or eigenfunctions) look like.

In the previous episodes we obtained various numerical FEM solutions for Helmholtz problems. Although we discussed their meaning in the previous episodes it is useful to discuss that again more deeply in a single page, which can act as a quicker reference. This episode will focus on the Helmholtz solver solution fields, while other episodes will focus on the output of other solvers. The Physical Meaning of a Solution Field The meaning of a solution field largely depends on the solver itself.