In the current version of 4coder(4.0.15), I am getting this pinging sound every time I click 'alt + [some_key]'. On 4coder(4.0.14), this never happened. This pinging sound happens with my key bindings and the default key bindings, so i am not sure where the problem happens. I am wonder whether this is a current issue or if it is only on my system.
This was a result of my reconfiguration of the input system without any audio device plugged into my computer. It will be fixed in the next build that I will try to get out soon. Although... the idea of making it optional had never occurred to me, but it's not a bad thought.