Opsgenie informs you about alerts with push notifications. You can customize sounds for each alert action, select an awakening sound for New Alerts and a different sound for Schedule Starts. These settings are accessible from My Profile -> Sounds.
Changing the default notification sound changes the sound setting for actions that are not modified before.
Custom sounds may not be played if permission of reading your personal sound file on your device is not configured. To avoid missing any sound notifications, please make sure that read permission is given to Opsgenie on your device.