Once you've connected your bluetooth headset to the iPad/iPhone, you can perform a volume check for audio notifications at any time.
Tap Settings > User Settings > Audible Notifications and Warnings
Tap on either Male or Female rows to hear a volume check.
The device volume setting during this demonstration will be recalled for use every time you use AvPlan. This is helpful for setting the volume within your headset when connected by Bluetooth.
You can find more detail on Audio notifications in the User Settings section of the User Manual