Wale
Automatic volume control for all individual apps in real time
CAUTION - Always pull down your speaker volume when update Wale or change your settings
Wale is an open-source app which means it's not verified with a commercial certification, hence, some sensitive AVs will alert Wale could be a virus. If you got such alert, please report to your AV provider or open a new issue. Anyway, You must run an app which you trusts only. So stop using Wale if you can't trust it.
Wale is distributed under MIT license, however it's restricted to my own codes...