### Acoustic-Structure Interaction with a Perfectly Matched Layer (PML)

This small tutorial model shows how to set up a model with a solid mechanics and a pressure acoustics domain including a common perfectly matched layer (PML). The PML is used to model an open or infinite domain for both the elastic waves and the pressure waves. Two configurations of PMLs exist (this model describes the first case which is also the most difficult to handle): 1. One PML should ...

### Acoustic Streaming in a Microchannel Cross Section

Recent advances in the fabrication of microfluidic systems require handling of live cells and other micro particles as well as mixing. All this can, for example, be achieved using acoustic radiation forces and the viscous drag from the streaming flow. Streaming: Due to the nonlinear terms in the Navier-Stokes equations, harmonic perturbation of the flow will lead to a net time-averaged flow ...

### Loudspeaker Driver in a Vented Enclosure

This model of a boxed loudspeaker lets you apply a nominal driving voltage and extract the resulting sound pressure level in the outside room as a function of the frequency. The sensitivity, both on-axis and spatial, is determined as function of frequency. These are some of the most important design parameters for a loudspeaker. The electromagnetic properties of the driver are supplied from the ...

### Helmholtz Resonator with Flow: Interaction of Flow and Acoustics

Helmholtz resonators are used in exhaust systems, as they can attenuate a specific narrow frequency band. The presence of a flow in the system alters the acoustic properties of the resonator and the transmission loss of the subsystem. In this tutorial model, a Helmholtz resonator is located as a side branch to a main duct. The transmission loss through the main duct is investigated when a flow ...

### Piezoelectric Tonpilz Transducer

The tonpilz (sound mushroom) piezoelectric transducer is a transducer for relatively low frequency, high power sound emission. The transducer consists of piezoceramic rings stacked between massive ends and pre-stressed by a central bolt. The tail and head mass lower the resonance frequency of the device. In this model the frequency response of the transducer when the bolt is not pre-stressed ...

### Anechoic Coating

Anechoic coatings are used for lowering visibility to sonars, for example on submarines. This model calculates the reflection, absorption, and transmission properties of an anechoic coating on a steel plate based on a setup from literature.

### Helmholtz Resonator Analyzed with Different Frequency Domain Solvers

This model simulates a simple three-dimensional axisymmetric Helmholtz resonator, a classic acoustics model of a resonating circuit with a known theoretical solution. The idealized version considered here consists of a tube and a closed volume in series which are exposed to a pulsatile pressure. Real-world phenomena explained by the resonator include amongst others the resonance from blowing ...

### Focused Ultrasound Induced Heating in Tissue Phantom

This model example shows how to model tissue heating induced by focused ultrasound. First, the stationary acoustic field in the water and the tissue are modeled to obtain the acoustic intensity distribution in the tissue. The absorbed acoustic energy is then calculated and used as the heat source for a Bioheat Transfer physics in the tissue domain in a time-dependent study simulating the ...

### Transient Gaussian Explosion

An ellipse with sound-hard walls has the interesting property that an acoustic signal emanating from one of the foci refocuses at the other focal point b/c seconds later, where b (in meters) is the major axis length and c (m/s) is the speed of sound. This model involves a Gaussian explosion at one focus of an ellipse to illustrate some properties of time-dependent acoustic problems. The ...

### Ultrasonic Flow Meter with Piezoelectric Transducers: Coupling between FEM and DG

Ultrasonic flow meters determine the velocity of a fluid flowing through a pipe by sending an ultrasonic signal across the flow at a skew angle. When there is no flow, the transmitting time between the transmitter and the receiver is the same for the signals sent in the upstream and downstream directions. Otherwise, the wave traveling downstream moves faster than the one traveling upstream, ...