It's really annoying especially in ground combat. You spam your weapon keys while fighting and because weapon is mostly not ready to fire you must hear always this "key-not-ready" sound.
I must disable my UI-sounds because of this what's bad because I can't hear tells incoming and can't also hear the other UI-sounds which I like.
Dev's, please remove this sound, in ground and in space
I'll admit this sound is annoying (both on ground and ships) And I should have to turn down the volume of an entire section just because of one sound (its a fine suggestion - just should have to do it that way)
There is an easy way to fix this: stop spamming your weapon keys in a fight.
Rather than just mashing the keys randomly as fast as possible, use the keys for the weapon that are ready. The game isn't running fast enough that there isn't time to check your cooldowns, and with practice you should find there is a rhythm and sequence to how the cooldowns complete that you can learn.