This is the best app to set 'per-app' volume on your Mac.

Following are the ways by which you can turn off the DING sound when changing Volume or at least avoid it. Change Volume from the Quick Action Menu Disable notification or alert sound for your wired ...

Google Home app has reinstated multi-speaker volume control, previously removed due to a lawsuit with Sonos. Users can now adjust the volume across multiple speakers using the app or voice commands.