## New Impedance Boundary Conditions for Acoustics Simulations

##### Søren Vedel December 3, 2015

When developing a new product or functionality, the first step is typically to understand the functional properties in isolation. To achieve reliable and accurate predictions via mathematical modeling, it is essential that the critical components, test setup, and boundary conditions are specified in great detail. Most engineers, however, would prefer to focus on the critical components rather than “irrelevant” boundary conditions. New impedance boundary conditions in the Acoustics Module of COMSOL Multiphysics help to close this gap.

Read More##### Guest Bernd Baumann November 11, 2015

Today, we introduce guest blogger Bernd Baumann, who shares insight into optimizing the performance of metal-halide lamps with simulation, with input from his colleague Joerg Schwieger. With the help of COMSOL Multiphysics, we investigated the impact of acoustic resonances and the related acoustic streaming field on the operation of metal-halide discharge lamps. To our surprise, we found that the lamps exhibit behaviors that are similar to a well-known mechanical system — the forced Duffing oscillator with a softening spring.

Read More##### Guest Lars Fromme November 6, 2015

Today, we welcome Lars Fromme back to the blog — this time as a guest blogger from the FH Bielefeld University of Applied Sciences. Working with loud machines is an occupational safety issue in the modern world. To keep workers safe, we can design low-cost solutions to control the noise with the help of simulation. Researchers at the FH Bielefeld University of Applied Sciences set out to do just that by simulating acoustic transfer paths with COMSOL Multiphysics simulation software.

Read More##### Alon Grinenko October 13, 2015

In our Acoustophoretic Force blog series, we have discussed the nature of acoustic radiation force and different ways to compute this force in the COMSOL Multiphysics® software. Today, we will introduce you to a related phenomenon, acoustic orbital angular momentum, and demonstrate how to model it.

Read More##### Mads Herring Jensen October 1, 2015

This past July, I had the pleasure of attending the 22nd International Congress on Sound and Vibration. In addition to running the COMSOL vendor booth with my Italian colleague Gabriele, I was also a presenter at the event. My presentation was based on a paper I wrote with Henrik Bruus and Jonas Karlsen that focuses on how to determine acoustic radiation forces including thermoviscous effects. Let’s explore acoustophoretic effects in greater detail and the research findings highlighted in my presentation.

Read More##### Linus Andersson June 15, 2015

The acoustic diffusion equation is the quickest and easiest way to model high-frequency acoustics. In fact, this method of acoustical analysis proved particularly helpful in planning the layout of my parents’ future home. I will introduce the topic of acoustic diffusion by sharing my own personal experience, while highlighting the assumptions behind this modeling approach, as well as its strengths and weaknesses.

Read More##### Alon Grinenko May 20, 2015

In an earlier blog post, we considered the computation of acoustic radiation force using a perturbation approach. This method has the advantage of being both robust and fast; however, it relies heavily on the theoretical evaluation of correct perturbation terms. The idea behind the method presented here is to solve the problem by deducing the radiation force from the solution of the full nonlinear set of Navier-Stokes equations, interacting with a solid, elastic microparticle.

Read More##### Guest René Christensen April 21, 2015

Today we welcome guest blogger René Christensen from Dynaudio A/S. When evaluating loudspeaker performance, dips and/or peaks in the on-axis sound pressure level can be a result of an unfortunate distribution of phase components. To overcome this, we use a phase decomposition technique that splits a total surface vibration into three components depending on how they contribute to the sound pressure in an arbitrary observation point; either adding to, subtracting from, or not contributing to the pressure.

Read More##### Chien Liu April 1, 2015

Over half a century ago, Mark Kac gave an interesting lecture on a question that he had heard from Professor Bochner ten years earlier: “Can one hear the shape of a drum?” He focused on the (then undetermined) uniqueness of the set of eigenvalues given the shape of a vibrating membrane. The eigenvalue problem has since been solved and here we explore the “hearing” part of the question by considering some interesting physical effects.

Read More##### Mads Herring Jensen February 25, 2015

When inside a room — a conference room, concert hall, or even a car — everyone has an opinion of when the “acoustics” are good or bad. In room acoustics, we want to study this notion of sound quality in a quantitative way. In short, room acoustics is concerned with assessing the acoustics of enclosed spaces. The Acoustics Module of COMSOL Multiphysics has several tools to simulate the acoustics of rooms and other confined spaces. I will present those here.

Read More##### Alon Grinenko January 29, 2015

Acoustic radiation force is an important nonlinear acoustic phenomenon that manifests itself as a nonzero force exerted by acoustic fields on particles. Acoustic radiation is an acoustophoretic phenomenon, that is, the movement of objects by sound. One interesting example of this force in action is the acoustic particle levitation discussed in this previous blog post. Today, we shall examine the nature of this force and show how it can be computed using COMSOL Multiphysics.

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