Pressure Reciprocity Calibration Coupler with Detailed Moist Air Material Properties

Application ID: 72031

When high-fidelity measurement microphones are calibrated, a pressure reciprocity calibration method is used. During calibration, two microphones are connected at each end of a closed cylindrical cavity. For the calibration procedure, it is important to understand the acoustic field inside such a cavity, including all the thermoviscous acoustic effects, for example, the acoustic boundary layers at higher frequencies and the transition to isothermal behavior at the lower frequencies.

This model sets up a simple calibration coupler model and discusses important considerations when performing a high precision absolute value simulation.The model results include the acoustic transfer impedance used for reciprocity calibration. The results are compared with analytical predictions valid at the low frequencies where the system is isothermal.

The model is further extended with precise material property estimation using the Thermodynamics functionality in COMSOL Multiphysics. This allows setting up a moist air material that depends on the ambient pressure, temperature, and relative humidity.

This model example illustrates applications of this type that would nominally be built using the following products: