Well I think I've read something about this, but can't recall where.
I'm thinking there are some issues regarding alert sounds such as buildings getting attacked or stuff getting finished(upgrades/production).
1) I'm not entirely sure which notifications exists in the game currently, but I can take two examples:
A ping sound when you get targeted by a tower, as well as a red line. This is fine but it took me a while to actually figure out what that ping sound was, and sometimes it can get a bit overwhelming if you're balancing on the edge of their range. Perhaps the red line is enough and no sound for that.
When your healing stuff is attacked it pings it on the minimap, this is confusing because for example I sometimes think it's a teammate calling for a "heal" or "back", especially since it triggers quite often from the long range celesta skill.
2) I don't think there's a notification from towers getting attacked, so you might not react when someone is pushing fast enough. Also I think there is a lack of notification when your army is under attack.
Overall I think the best notifications in general is a voice saying "army under attack" or "your base is under attack" or "research complete" coupled with some map indicator. I really don't like the "PING" sound effect when something is under attack.
To sum it up, the whole system could use some love. Make it more consistent and intuitive, so you don't have to figure out which sound is referring to what.