Acoustic Model Module
The Acoustical Modeler provides the ability to predict the behaviour of an acoustical system using advanced lumped parameter techniques. Lumped parameter modelling has been used in acoustics for many decades, leveraging the abilities of electrical modelers. However, electrical simulators are significantly limited in their ability to approximate and acoustical system, and the results are not presented in meaningful acoustical terms. The Ares Acoustic Modeler is a dedicated acoustical solver with many features that make it extremely easy and convenient to use.
One immediate apparent feature of the Modeler when you start using it is that you work with real acoustical icons, such as the speaker, volume and circular port elements shown below. You’ll also work with meaningful units such as mm and SPL.
The Modeler is a multi-physics solver that includes components such as
These can be connected together to form a single model that combines the three major elements types together. For instance, the model below shows a discrete model for a moving coil speaker mounted in a box, with its front cone surface radiating through a circular port.
Also, all major ITU ear simulators are represented. The model below shows a very simple earpiece or headphone model that directly drives an ear simulator. Any arbitrary topology is possible.
Viscous and Thermal Losses in Narrow Ports
When sound propagates through narrow openings (i.e. ports), the viscous drag of the acoustic air flow against the sides of the port wall will add a significant amount of resistive drag to the air flow. Also, the acoustic compression/rarefaction process generates heat that’s conducted into the port walls, causing further energy loss to the acoustic process. The Modeler properly handles these effects in the circular and rectangular port elements. These effects are frequently approximated due to the difficulty of evaluating the fundamental acoustical equations that describe their effects. However, Ares does not use any such approximations but fully evaluates the governing equations.
Ports: 1D waveguides
It is common to model a port as a simple mass reactance, but the Ares Modeler takes the full effect of standing waves into account, essentially treating ports as one-dimensional waveguides. Also, since the thermal and viscous effects are properly handled, the lossy nature of these waveguides as the cross-section area becomes small is properly handled. This is critical for properly predicting the damping around a resonance. It also allows for the design of acoustic resistors by decreasing port diameters.
Automatic End Corrections
Unlike electrical components, acoustical components couple to each other through extra mass reactance at area changes. This mass reactance is traditionally handled through end corrections which artificially extend the lengths of ports. When manually building a lumped parameter model, the engineer must manually add the appropriate end correction to the elements. An experienced engineer will at best find this tedious, and a novice can completely forget the need to add them. The Ares Modeler automatically handles the end corrections, making the Modeler easier to use and helps the novice avoid the mistake of not including them. The end correction is applied to all appropriate acoustical elements, including volumes and radiating elements. This is simply not possible when using standard PSpicemodelers.
Iterating on a parameter
An extremely useful feature is the ability to quickly perform a parameter sensitivity study by iterating on a parameter. By pressing the […] button to the right of the Vol parameter in the model below, the response at the ear canal can be seen as a function of different rear speaker volumes.
This response is shown in the figure below. Parameter iteration allows you to quickly see that the volume has a great deal of effect on the low frequency response, but very little on the high frequency response. This feature becomes extremely useful as model complexity grows.
Variables and Parametric Modelling
The Modeler allows you to create a list of variables that can be used in the element parameters entries. Complex equations can also be entered for the parameter values, creating the ability to easily generate parametric design studies.
The graph element allows for up to 26 result buffers (A-Z) to store modelling results, and compare them to alternative design possibilities. Measured results from the Frequency Response and Flow Impedance Measurement models can also be imported into the graph elements for direct validation of modelled results with experimental data. Many graph options are provided, including linear or log graphs, dB or linear magnitudes, real and imaginary formatting, standard A-C weighting as well as P50 speech and psophometric noise weightings.
Graph data can be quickly copied to the clipboard by simply clicking on a graph, or the entire frequency dependent complex values (pressure & volume velocity, force & velocity) can be exported for easy analysis in other programs.
The model results are plotted in useful units such as SPL. The modeler will also plot displacement, so the excursion of a speaker can easily be seen. Both volume velocity (m^3/s) and particle velocity (m/s) are plotted, to provide the use with better insight into the acoustical system.
The graph element’s major plotting options are shown in the controls below.
A screen capture showing all of the elements presently supported is shown below. These include membranes, horns, radiation elements, and directional microphones.
Keep It Simple
Keeping the Modeler interface simple is a key part of its design. Finite and boundary element analysis (FEA/BEA) are powerful analysis tools, but to be effective, they require expert users whose major occupation is to operate those programs. The Ares Modeler is meant to be accessible to novice as well as expert users, quickly providing information about the acoustical behaviour of a system with minimal effort. When used properly, the Modeler can provide almost instant feedback about your design and help you choose the direction to take it to improve its performance.
As future acoustical problems are considered, keeping the interface simple and accessible will be key.
This “keep it simple” approach is applicable to a variety of problems.
Custom elements for specific customers are also an available option. It is common for companies to invest considerable time into generating complex models for their devices, such as a MEMS torsional accelerometer, or microphone. However, these internal models frequently lack good user features to make them accessible to engineers other than the original model designer. We would be happy to create a new “custom” element that would implement these custom elements and make them only available for your company’s usage if needed.