Efficiently Calculating the Acoustic Transfer Impedance of a Perforate

Linus Andersson | September 29, 2016

Perforations, in mufflers for example, enable partial sound transmission between chambers as well as in and out of pipes. When simulating perforates, it’s possible to draw and mesh each hole, but this increases the time it takes to solve the model. For a more efficient approach, we can apply a semitransparent boundary. Here, we’ll discuss several techniques for doing so as well as describe a method for computing the transfer impedance of the perforate.

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Linus Andersson | March 15, 2016

Over the 10th through 18th centuries, the sound holes in violins evolved from a circular shape to an elongated f shape. In a recent research paper, MIT scientists and violin makers from the North Bennet Street School in Boston investigated the effects of this change in shape. They suggest that the f-shaped holes increase the air flow, making the bass notes of the violin twice as loud. Today, we will reproduce their findings with COMSOL Multiphysics.

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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.

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Linus Andersson | December 18, 2014

No matter how much you refine the mesh at that corner in your geometry, the electromagnetic field that you are computing never seems to settle on a converged value. Is that a problem? If so, what can you do about it? Read on to find out.

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Linus Andersson | September 15, 2014

Picture yourself on a deserted beach, eyes closed and just listening. It’s a windy day in September. Seagulls circle around a rock formation, the waves break up into foam. It starts to rain, so you record a sound snippet on your cell phone for later. You consider playing the clip on your car stereo, but you don’t, because you know it just isn’t the same thing. Besides the breeze and the ocean smell, what’s the difference? Let’s talk room acoustics.

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Linus Andersson | December 11, 2009

As most skilled COMSOL users, I am sure you know that you are not limited to just selecting what is in our drop-down lists. Say that you have invented your own measure of structural stress. You want it to be equal to the quadratic mean of the Tresca and von Mises stresses. Go to Plot Parameters to find out what these predefined stresses are called (tresca_smsld and mises_smsld if you are modeling in 3D with the Structural Mechanics Module). Now […]

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