An actuator rail assembly for conveying an actuating fluid under pressure to at least one fuel injector includes an elongate fluid passageway (18) being defined in a rail (12). A fluid inlet port (31) is in fluid communication with the fluid passageway (18), the inlet port being fluidly couplable to a source of actuating fluid under pressure. A respective fluid outlet port is associated with each respective fuel injector and being fluidly couplable thereto for conveying actuating fluid to the respective fuel injector and at least one fluid cavity (16) having at least one throttling orifice (14), the orifice effecting fluid communication between the fluid cavity (16) and the fluid passageway (18). An acoustic wave attenuator and a method of attenuation are also included.