The variable speed vibroacoustic simulation of the SPMSM has been set-up in the project *tuto_SPMSM_01*. This article details the main graphical post processing available in command line once a variable speed simulation is completed.

All the variable speed graphical post processing start with *plot_VS*, they can be accessed with by using the Matlab auto-completion or in the post_processing documentation.

The variable speed average radial acceleration can be displayed as a spectrogram with plot_VS_Ar_spectrogram

If you are not familiar with this graph you can refer to our detailed article on what is a spectrogram?. One can see that significant vibration occurs at 5000 and 6500 rpm.

The overall SPL (sound pressure level) can be displayed with plot_VS_ASPL_overall

The red line corresponds to the speed above which the spectrum is complete up to specified maximum frequency Input.Simu.freq_max_spec.

To further understand where resonances come from, one can plot the sonagram (variable speed noise spectrum) with plot_VS_ASPL_sonagram

The contribution of the structural modes to the acoustic noise level can also be checked with (plot_VS_ASWL_modal_cont) :

The following resonances occur (fs is the fundamental electrical frequency and fR is the rotation mechanical frequency):

- mode (0,0) (breathing mode) of the stack is excited at 2*6235 rpm by an harmonic force at 36fs=LCM(Zs,2p)fR
- mode (0,0) (breathing mode) of the stack is excited at 6235 rpm by an harmonic force at 72fs=2LCM(Zs,2p)fR
- mode (4,0) of the stack is excited at 11010 rpm by an harmonic force at 16fs=LCM(Zs,2p)fR-2fs
- mode (4,0) of the stack is excited at 8795 rpm by an harmonic force at 20fs=LCM(Zs,2p)fR+2fs
- mode (4,0) of the stack is excited at 5180 rpm by an harmonic force at 34fs=2LCM(Zs,2p)fR-2fs
- mode (4,0) of the stack is excited at 4628 rpm by an harmonic force at 38fs=2LCM(Zs,2p)fR+2fs