# Multi-Reference Mode Indicators

As part of the Multi-Reference Modal Analysis option, both Multi-Reference CMIFs (Complex Mode Indicator Functions) and Multi-Reference MMIFs (Multivariate Mode Indicator Functions) are added to the Mode Indicator methods list on the Mode Indicator tab.

A *peak* at or *near the same frequency* in two or more Multi-Reference Indicator curves indicates *closely coupled modes* or *repeated roots*.

CMIFs Indicating Two Closely Coupled Modes Near 200 Hz.

## Multi-Reference CMIF

The Multi-Reference CMIF curves are calculated by performing a *singular value decomposition* of multi-reference FRF data, resulting in a separate CMIF curve *for each reference*.

*Each* *peak* on *each* CMIF curve is an indication of a resonance.

## Multi-Reference MMIF

The Multi-Reference MMIF curves are calculated by performing an *eigensolution* of multi-reference FRF data, resulting in a separate MMIF curve *for each reference*.

*Each* *peak* (*or valley*) on *each* MMIF curve is an indication of a resonance.

## Modal Participation Factors

The Multi-Reference CMIF & MMIF calculations also provide M*odal Participation Factor* curves for each reference of FRF data.

Modal participation factors are used to *weight* each reference of data during Multi-Reference curve fitting.