WWise Plugins
From CCRMA Wiki
You will find the effect plugin and source plugin documentation in:
Wwise SDK Documentation: Wwise SDK 20XX.X - Windows » Going Further » Creating New Plug-ins
You can also find sample effects in: C:\Program Files (x86)\Audiokinetic\Wwise v20XX.X build XXXX\SDK\samples\Plugins
The AkDelay would be a good start.
https://www.audiokinetic.com/resources/project-samples/
https://www.audiokinetic.com/products/wwise-add-ons/
http://www.audiokinetic.com/download/documents/Wwise_GetStartedGuide.pdf