All on the Client Config tab Notifications:

• Enable Notifications (master switch; when No, the live feed reports "Notifications are currently disabled").
• Enabled Notification Types — multiselect; keep Orders (created, paid, cancelled, refunded) to receive order alerts.
• Enable New Notifications Sound and Notifications Sound File (upload your own audio).
• Enable New Notifications Side Popup and Enable New Notifications Side Popup On Mobile.
• Enable System Notifications — native browser notifications (requires HTTPS and the browser's permission; on iPhone/iPad only when the admin is installed as a home-screen app).

On mobile the sound is "primed" on the first tap, so staff must touch the screen once after loading a page before sounds will play.