Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.
Simulation of the acoustics inside a sedan, including sound sources at the loudspeaker locations.
The Acoustics Module is designed specifically for those who work with devices that produce, measure, and utilize acoustic waves. Application areas include speakers, microphones, hearing aids, and sonar devices, to name a few. Noise control can be addressed in muffler design, sound barriers, buildings, and room acoustics applications.
Straightforward user interfaces provide tools for modeling acoustic pressure wave propagation in air, water, and other fluids. Dedicated modeling tools for thermoviscous acoustics enable highly accurate simulation of miniaturized speakers and microphones in handheld devices. You can also model vibrations and elastic waves in solids, piezoelectric materials, and poroelastic structures.
Multiphysics interfaces for acoustic-solid, acoustic-shell, and piezo-acoustics couplings bring your acoustic simulations to a new level of predictive power. Aeroacoustic problems can be modeled using one of several linearized equation approaches. Room and outdoor acoustics problems can be modeled using ray tracing or acoustic diffusion methods.
By using realistic simulations in 1D, 2D, 2D axisymmetry, or 3D, you can optimize existing products and design new products more quickly. Simulations also help designers, researchers, and engineers to gain insight into problems that are difficult to handle experimentally. By testing a design before manufacturing it, companies save both time and money.
The sound level from a car depends to a great extent of the quality of the muffler. Over the years, researchers in the car industry have struggled to produce mufflers that are efficient from both an acoustic and an environmental perspective.
This model describes the pressure wave propagation in a muffler for an internal combustion engine.
The model also shows how to analyze both inductive and resistive damping in pressure acoustics.
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 heating and cooling of the tissue when exposed to ultrasound for 1 second.
This model is suitable for tissue heating when the acoustic pressure at the focus is well below acoustic cavitation threshold.
The modeling of aircraft-engine noise is a central problem in the field of computational aeroacoustics. The acoustic field in a model of an axially symmetric aero-engine duct, generated by a noise source at the boundary, is computed and visualized.
Results are presented for situations with as well as without a compressible irrotational background flow and for the cases of hard and lined duct walls.
A surface acoustic wave (SAW) is an acoustic wave propagating along the surface of a solid material. Its amplitude decays rapidly, often exponentially, through the depth of the material.
SAWs are utilized in many kinds of electronic components, including filters, oscillators, and sensors. SAW devices typically apply electrodes to a piezoelectric material to convert an electric signal into a SAW, and then back again. The SAW response provides the information that the device is used to collect.
This model investigates the resonance frequencies of a SAW gas sensor. The sensor consists of an interdigitated transducer etched onto a piezoelectric substrate, covered with a thin film. The mass of the film increases as its material selectively adsorbs a chemical substance from the air. This causes a shift in resonance to a slightly lower frequency and thus information about the amount of species in the air.
In this model, two fluids are separated by a solid elastic structure. An acoustic pressure wave impacts the structure resulting in a reflected wave and a wave transmitted with a loss through the structure. This model investigates the transmission loss through the structure. The effects of incident angle, frequency, and dampings are studied.
Important features used: Acoustic-structure interaction with arbitrary incident angle, scattered field formulation, the perfectly matched layer (PML), and periodic Floquet boundary conditions.
Ref: S. Dey and J. J. Sirron, Proceedings of IMECE 2006, ASME 2006 International Mechanical Engineering Congress & Exposition, Chicago, USA.
Knowing the velocity of a moving fluid is important in all cases where the fluid is used to transport material or energy. In the time-of-flight or transit-time method for determining flow velocity, an ultrasonic signal is transmitted across the main flow in a pipe to noninvasively determine its velocity. By transmitting the signal at an angle relative to the main flow, the ultrasound signal will travel faster than the speed of sound if it moves in the direction of the main flow, and slower than the speed of sound if it moves against it. The difference in travel times in the two directions increases linearly with the velocity of the main flow. Flow meters of this type find many uses, particularly in industrial settings.
In this tutorial model, learn how to simulate a generic wetted transient-time ultrasound flow meter with COMSOL Multiphysics® simulation software. The model setup solves the transient problem of a signal traversing the flow downstream. First, we use the CFD Module to calculate the steady-state background flow in the flow meter. The signal moving upstream is precalculated and imported as data. The difference in arrival times is used to estimate the velocity of the main flow. Next, we use the Convected Wave Equation, Time Explicit physics interface, found under the Ultrasound node in the Acoustics Module. This interface is tailored for transient high-frequency situations and is based on the discontinuous Galerkin method (DG-FEM).
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, work also at low frequencies.
A typical automotive exhaust system is a hybrid construction consisting of a combination of reflective and dissipative muffler elements. The reflective parts are normally tuned to remove dominating low-frequency engine harmonics while the dissipative parts are designed to take care of higher-frequency noise.
The muffler analyzed in this model, is an example of a complex hybrid muffler in which the dissipative element is created completely by flow through perforated pipes and plates.
This is a model of the acoustics inside a sedan, that is inside a typical hard-top family car. The model sets up sources at loudspeaker locations as well as impedance conditions to model soft absorbing surfaces (seats and carpet).
The model results in plots of the pressure, sound pressure level, and intensity inside the car. The frequency response at given points inside the cabin are also determined.
Designing structures and open spaces with respect to sound quality is important for concert halls, outdoor environments, as well as the rooms of a house. You can simulate acoustics in the high-frequency limit, where the wavelength is smaller than the geometrical features, with ray acoustics.
This application analyzes the acoustics of a small concert hall using the Ray Acoustics physics interface. Users of the app can define a microphone location to measure the impulse response, an omnidirectional sound source, wall absorption parameters, and the properties of diffusers. The results include a filtered energy impulse response for a given Fourier component.
It is often not possible to insert a normal microphone directly into the sound field being measured. The microphone may be too big to fit inside the measured system, such as for in-the-ear measurements for hearing aid fitting. The size of the microphone may also be too large compared to the wavelength, so that it disturbs the acoustic field. In these cases, a probe tube may be attached to the microphone case in order to distance the microphone from the measurement point. In this model, the effect on the microphone’s sensitivity due to the addition of this small probe will be investigated.
This is a time-dependent model of a generic probe tube microphone setup consisting of an external acoustic domain, an elastic probe tube, and the cavity in front of the microphone diaphragm. The probe tube, modeled using the Pipe Acoustics, Transient physics interface, is connected to two separate 3D pressure acoustics domains, leading to a fully coupled acoustics simulation. This model requires the Pipe Flow Module.
