# Dynamic Boundary Conditions - "Quiet" Boundaries **URL:** \ **Category:** FLAC3D\ **Created:** [June 20, 2022, 8:45pm UTC](https://forum.itascainternational.com/t/dynamic-boundary-conditions-quiet-boundaries/628 "2022-06-20T20:45:31Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![CrissBidermann](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@CrissBidermann](https://forum.itascainternational.com/u/CrissBidermann)\ **Post date:** [June 20, 2022, 8:45pm UTC](https://forum.itascainternational.com/t/dynamic-boundary-conditions-quiet-boundaries/628/1 "2022-06-20T20:45:31Z")
The differentiation and application of the following commands is not very clear to me: zone face apply quiet-normal zone face apply quiet-dip zone face apply quiet-strike ---
**Author:** ![natalia.aravena](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.itascainternational.com/natalia.aravena/32/104_2.png) [@natalia.aravena](https://forum.itascainternational.com/u/natalia.aravena)\ **Post date:** [June 23, 2022, 6:57pm UTC](https://forum.itascainternational.com/t/dynamic-boundary-conditions-quiet-boundaries/628/2 "2022-06-23T18:57:10Z")
Hi Criss! In static analysis, fixed (or elastic) boundary conditions may be realistically imposed at some distance from the region of interest, but in dynamic analysis, these conditions cause reflection of waves propagating into the model. The solution to this problem is through the use of viscous boundary conditions, which by definition prevent the reflection of waves on their surface. quiet Commands: ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/85ae604b34394ff66252fc72faf1c2044ea041b4.jpeg) ![image](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/d38332cda877e1ca01f4ec1d78f12389ac4fa22f.jpeg) I would recommend checking out the example in the manual. Dam Foundation.