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Muffler with Perforates
Reflective mufflers are best suited for the low-frequency range where only plane waves can propagate in the system, while dissipative mufflers with fibers are efficient in the mid- to high-frequency range. Dissipative mufflers based on flow losses, on the other hand, also work at low frequencies. A typical automotive exhaust system is a hybrid construction consisting of a combination of ...
Optimizing the Shape of a Horn
A plane-wave mode feeds an axisymmetric horn radiating from an infinite baffle towards an open half space. The radius of the feeding waveguide is assumed to be fixed, as well as the depth of the horn and the size of the hole where the horn is attached to the baffle. By varying the curvature of the initially conical surface of the horn, its directivity and impedance can be changed. This model ...
Acoustic Muffler with Thermoviscous Acoustic Impedance Lumping
This model utilizes the thermoviscous acoustic interface in a sub-model to obtain detailed results for the transfer impedance of a perforated plate (including the thermal and viscous losses). The impedance is in turn used as an internal impedance in a pressure acoustic model of a muffler. The results are compared to classic impedance models and measurements.
Acoustic-Structure Interaction and Air Flow in Violins
These models are featured in the blog post [Analyze Violin Tone and Volume with Multiphysics Modeling](http://www.comsol.com/blogs/analyze-violin-tone-and-volume-with-multiphysics-modeling/). One applies acoustic-structure interaction to study how the air mode resonance is affected by the coupled vibrations in the violin body. The other uses a potential flow approximation to find out how the air ...
Spherical Piezoacoustic Transducer
This tutorial provides a step-by-step instruction to setup a fully-coupled 3D structural-acoustic interaction problem. Interaction between a vibrating spherical piezoelectric structure with the surrounding fluid media is considered. The piezoelectric material PZT-5H from the materials library is used. Instructions on how to create a radially polarized piezoelectric material in spherical ...
Noise Radiation by a Compound Gear Train
Predicting the noise radiation from a dynamic system gives designers insight into the behavior of moving mechanisms early in the design process. For example, consider a gearbox in which the change in the gear mesh stiffness causes vibrations. These vibrations are transmitted to the gearbox housing through shafts and joints. The vibrating housing further transmits energy to the surrounding fluid, ...
Acoustic Reflections off a Water-Sediment Interface
This model determines the reflection coefficient of plane acoustic waves, at different frequencies and at different angles of incidence, off a water-sediment interface. The ability of the Poroelasitc Waves interface to model the coupled acoustic and elastic wave in any porous substance (Biot's theory) is used to describe the water-sediment system. The model results are in good agreement with ...
Acoustic Reflection Analyzer for a Water-Sediment Interface
Analyzing acoustic reflections at surfaces of various structures is important for many engineering disciplines. The Acoustic Reflection Analyzer for a Water-Sediment Interface app shows one such system where the analysis has relevance for underwater acoustics and sonar applications. The app analyzes the reflection and absorption coefficients of plane acoustic waves, scattering off of a water ...
Gaussian Pulse Absorption by Perfectly Matched Layers: Pressure Acoustics, Transient
This tutorial simulates a standard test and benchmark model for perfectly matched layers (PMLs) as absorbing boundary conditions in the time domain. It involves the propagation of a transient Gaussian pulse with no flow. The _Pressure Acoustics, Transient_ interface is used together with PMLs to reduce the computational domain and suppress the reflections from the artificial boundaries. An ...
Organ Pipe Design
The Organ Pipe Designer allows you to study the design of an organ pipe and then play the sound and pitch of the changed design in a user-friendly app. The pipe sound includes the effects of different harmonics with different amplitudes. The organ pipe is modeled using the Pipe Acoustics, Frequency Domain interface in COMSOL Multiphysics. The simulation app allows you to analyze how the first ...
