The hard-sound gun was a sonic weapon that used "hard" sound to injure, disorientate, and incapacitate opponents.
Finding a wide usage as an anti-Force-sensitive weapon, hard sound guns produced an incredibly loud sonic shriek designed to overload the auditory nerves, causing immense pain and disorientation on the target. Consisting of small hand-held antenna, the hard-sound gun was a weapon that produced a focused and directional cone of hard sonic energy, capable of bursting eardrums, and even knocking over astromech droids. So powerful was this sound, it was capable of causing pain even after an ear had been burst, and was described as having an iron bar smack you in the face.
During the Clone Wars, hard-sound guns were deployed by the A-series assassin droids carried by Asajj Ventress against Jedi Jai Maruk and Jedi Master Maks Leem to great effect. The sound was so powerful and debilitating as to make Leem, a Jedi master, drop her lightsaber. While both Jedi were momentarily incapacitated, eventually, several minutes later they were able to overcome their pain and destroy the devices, and the droids.
Decades later, in 40 ABY at the start of the Second Galactic Civil War, at least one pair of astromech droids were modified to carry similar sonic weapons to defend Centerpoint Station against Jedi saboteurs. These did not burst Human eardrums, and may have been designed more for incapacitating opponents than injuring them. It was effective against any kind of opponent.