> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Natural Frequency Constraint

Define a natural frequency constraint for optimization to generate shapes with natural frequencies that lie inside or outside the specified range.

### Inputs

| Name            | Type                                                                                | Description                                                                                                                                               |
| --------------- | ----------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Number of modes | [Integer](../../../../block-documentation/types/integer)                            | Number of modes that will be searched for and included in the constraint computation.                                                                     |
| Band type       | Inside or Outside Enum                                                              | This defines whether the natural frequency of the optimized shape lies inside or outside the range defined by the Min Frequency and Max Frequency inputs. |
| Min frequency   | [Scalar](../../../../block-documentation/types/scalar)                              | The lower bound of the natural frequency range.                                                                                                           |
| Max frequency   | [Scalar](../../../../block-documentation/types/scalar)                              | The upper bound of the natural frequency range.                                                                                                           |
| Load case       | [Boundary Condition List](../../../../block-documentation/types/boundary-condition) | Load case for the constraint.                                                                                                                             |

### Outputs

| Type                                                                         |
| ---------------------------------------------------------------------------- |
| [Design Constraint](../../../../block-documentation/types/design-constraint) |