Each version of this integration matches a specific build of Unreal Engine 4. Here is what has changed between the 2017.1.8.6488.843 and the 2017.1.9.6501.856 release of the integration (in addition to upgrading to the new Unreal build).

Unreal Engine 4.15/4.16/4.17/4.18/4.19 - Wwise 2017.1.9.6501.856

• No updates to the Unreal Integration for Wwise 2017.1.9.