Simulate Acoustic Absorption Parameters
AcoustoDict
How well does a material absorb sound? How does it behave at different frequencies? Questions like these are crucial when it comes to developing high-performance acoustic materials - whether for vehicles, buildings, or aircraft. Simulations with the AcoustoDict module in GeoDict provide the answers.
AcoustoDict simulates the acoustic properties of porous materials using either a modeled material geometry or a CT scan. This module calculates important acoustic parameters that accurately describe the material's behavior, such as sound absorption coefficient, permeability, tortuosity, porosity, and thermal and viscous characteristic length.
These parameters serve as input data for proven analytical models – the Delany-Bazley model for highly porous materials or the Johnson-Champoux-Allard model for complex pore geometries. Using these models, AcoustoDict quickly and reproducibly calculates the frequency-dependent acoustic absorption curve of the material without a physical test setup.
Pore-scale acoustic analysis in AcoustoDict
The simulation component computes the effective
parameters in 3D geometries of porous materials
to predict the sound absorption coefficient across
a user-defined frequency range.
(a) 3D geometry of an air filter
(b) Sound absorption curve over a user-defined
frequency range
Material Database in AcoustoDict
The Material Database in GeoDict stores absorption curves derived from simulations or direct measurements for each material at various compression levels, enabling interactive prediction and comparison of acoustic performance.
Match function in AcoustoDict
The Match function in the Material Database automatically identifies the material whose stored absorption curve best matches a user-specified target, while accounting for compression effects.
Stack function in AcoustoDict
Mimicking an impedance tube setup, the Stack function predicts the overall acoustic absorption of a customizable multilayer (sandwich) configuration by interactively adjusting the arrangement and thickness of up to four layers.
Pore-scale acoustic analysis
GeoDict works with the resolved 3D geometry of porous materials. Using this pore-scale resolution representation, the simulation component of AcoustoDict computes effective parameters to predict the sound absorption coefficient across a user-defined frequency range. One such effective parameter is the static air flow resistance, obtained by solving the Stokes equations in the pore space of the material to determine the flow field.
Depending on the geometry of the porous material, the user can select an appropriate acoustic model to accurately predict the frequency-dependent sound absorption coefficient. For highly porous materials, the Delany–Bazley (DB) model is used. For materials with complex pore geometries, the Johnson–Champoux–Allard (JCA) model is used. For the JCA model, AcoustoDict determines the viscous characteristic length by solving a diffusion equation in the material's pore space.
Material Database
The Material Database component stores absorption curves obtained from simulations or direct measurements for later use. For example, multiple absorption curves at different degrees of compression can be stored and compared for nonwovens, which are often compressed to a given thickness as part of an acoustic material fabrication process. Then, the absorption curves for other degrees of compression can then be predicted interactively from the given data.
Stack function
The Stack function in the Material Database mimics the measurement process of a traditional impedance (Kundt’s) tube, where a plane sound wave is directed at a specimen and the sound absorption coefficient is determined from the measured incoming and reflected sound. Similarly, the Stack function predicts the acoustic absorption of a sandwich configuration - comprising up to four layers of different materials, including air gaps. Each layer's arrangement and thickness can be adjusted individually, and the overall absorption curve is updated interactively.
GeoDict Online User Guide
Following modules are often used in combination with AcoustoDict:
| Import & Image Processing | ImportGeo-Vol | |
| Image Analysis | ||
| Material Modeling | FiberGeo | |
| Simulation & Prediction | ||
| Interfaces |
Suitable modules depend on the specific application.