# Peak Pick

A parameter estimation technique where the peak value of the imaginary part of the frequency response function is used to estimate the mode shape value at that point. The phase is given by its sense (positive or negative).

This method is also known as quad picking since the value is being picked off the imaginary or quadrature part of the frequency response function.

**See also: **Frequency Response, Imaginary Number.

**Subjects: ** Noise & Vibration