The Grid Participation utility calculates the fluid grid participation based on the fluid node id information, which is essentially the raw participation information.  The raw participation information is not in the correct form for the contour plot however, because it has been scaled by the surrounding element areas.  The element area information is therefore removed when the fluid grid participation is calculated, and as a result an area neutral plot is returned (which is a true grid participation plot that is not dependant on the element size).

The results data is then projected on to the response of the grid (which is typically the driver’s ear response).  After the projection is completed, the in-phase portion (red/positive value) and out-of-phase (blue/negative value) portion of the contributions are displayed:

These two components allow you to look for the particular area of the structure which has the most positive (in-phase) contributions and also the area that has the most negative (out-of-phase) contributions.  You can then effectively reduce the acoustic response at a grid point by reducing the vibration/contribution coming from the positive/in-phase area, or by increasing the vibration/response in the negative contribution area.  Using either method will allow you to achieve the same result.

Finally, all of the participation results are scaled by the absolute value of the largest participation for each frequency.