Hard sound rifle

A Hard Sound Rifle is a Human-made sonic weapon. As it utilizes concentrated sound waves instead of a solid projectile, a hard-sound rifle leaves no residue or powder burns and causes little noticeable external damage to the intended target, making the weapon virtually untraceable. A preferred weapon used for assassinations by the Office of Naval Intelligence, they are sometimes (illegally) purchased by civilians for less malevolent means.

Although sonic weaponry does not appear in Halo: Combat Evolved, Halo 2, or Halo 3, it is mentioned prominently in I Love Bees. When an ONI assassin disguised as a homeless man is sent to kill Rani Sobeck for her investigation into a covert evacuation of the human colony of Troy, a protective detail dispatched by Colonel Herzog eliminates the operative through use of a hard-sound rifle. Having fallen off the roof to the street below, local authorities dismissed the death as an accident resulting from use of alcohol or drugs.