When averaging, the pressure or power is averaged before transformation to the dB scale. By selecting Edge, Boundary, or Domain, the input is automatically averaged. The data can be directly taken from a point in the model if, perhaps, a sensitivity is measured at a specific location. The Geometric entity level drop-down menu enables you to select how the input data is picked up from the model. An Overview of the Different Options and Settings Geometric Entity Level In the next section, we will explain its different options and settings in detail. The screenshot below shows the user interface (UI) for the Octave Band plot. Furthermore, this plot type makes it much easier to compare results with measured data, which is often given in octave or 1/3-octave bands. For the input to the plot, you can modify it to represent amplitude (e.g., the absolute value of a pressure), power (e.g., the power of incoming or outgoing modes at ports or an intensity integrated over a surface), or a general transfer function.Īll of these options help to simplify postprocessing considerably. You can also easily add weighting to the response curve, with the choice of a Z-, A-, C-, or user-defined weighting. The band format can represent the band power or band-average power spectral density (PSD), while the continuous curve represents PSD data.
With regards to the data fed to the plot, you can use any global quantity, or readily pick it up at a point or as an average over a line, surface, or volume.įor the graphs, you have the option to format the results so that they render in either bands (octaves, 1/3-octaves, or 1/6-octaves) or as a continuous curve. The output of the plot is automatically given on the dB scale, with several formatting options. The Octave Band plot, available in the Acoustics Module add-on to COMSOL Multiphysics ®, includes built-in features specific to acoustics simulations that can be helpful for representing and analyzing frequency-domain data. The Octave Band Plot, a Simple and Versatile Acoustics-Specific Plot
In the same way, the human ear also has a logarithmic sensitivity to sound magnitude, hence the use of a decibel (dB) scale for sound pressure levels.Īs we will describe next, the Octave Band plot includes more functionality than simply plotting acoustic responses in octave bands. Physiologically, such representation is motivated by the fact that the human ear itself filters (via auditory filters) and perceives sound on a logarithmic frequency scale. This visualization technique is closely related to specifications in standards and, thus, the way measurement equipment works (e.g., sound level meters). Representing an acoustic response by binning the signal energy into octaves, or fractional octaves, is very common for acoustic and audio engineers. Applying this concept results in bands of equal width on a logarithmic frequency axis. When discussing an octave, we are referring to a frequency band in which the upper frequency is twice the lower frequency. It has since been updated to reflect new features and functionality available in the Acoustics Module. Let’s learn a bit more about the Octave Band plot while highlighting its various options and settings.Įditor’s note: The original version of this post was published on January 21, 2016. The Octave Band plot provides you with an easy and flexible way to represent simulation results that are essential when modeling acoustics applications, including frequency responses, transfer functions, sensitivity curves, transmission losses, and insertion losses.
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