The Inverse Numerical Acoustics module provides a special procedure in which the usual ‘forward’ boundary element solution is reversed: it computes a set of surface vibrations which are the most likely cause of known acoustic pressures measured in the field.
The surface vibrations can be found at multiple frequencies and in multiple load cases based on the ATV (Acoustic Transfer Vector) technology. Linear or spline interpolation methods enable the ATV coefficients to be found at frequencies between the ones originally computed and stored, without any more computations.
The inverse solution itself uses Singular Value Decomposition techniques, controlled by the user to specified tolerances. Further enhancements in solution speed and accuracy can be obtained, if the vibrations are known (typically zero) on certain parts of the radiating surface: these known values can be defined or imported into the LMS SYSNOISE model, thereby reducing the size of the unknown inverse problem to be solved.
Inverse Numerical Acoustics complements other methods such as Acoustic Holography and Airborne Source Quantification. There are no limitations on the number or location of field points which can be used for measured pressures, nor on the number of elements or the mesh geometry, making it a very powerful technique in problem-solving diagnostics. Typical application areas include engine noise, tire noise and gear box noise.
