Visually asymptomatic patients with orbital fractures do not have ocular injury requiring emergent evaluation.

Aircraft ground operations and maintenance personnel can be exposed to whole-body vibration via the airborne transmission of acoustical energy. The purpose of this study was to characterize human body vibration response during exposures to airborne vibration generated by military fighter aircraft during high-power ground engine runs. Miniature triaxial accelerometers were mounted on the head (bitebar), chest, spine, and lower leg of the subject. Measurements were made for selected locations along a line parallel to the longitudinal axis of the aircraft at specified engine-power settings. The highest accelerations occurred in the fore-and-aft (X) chest response. One-third-octave analysis showed a distinct peak in the chest between 50 and 100 Hz not observed in the noise levels, strongly suggesting the presence of a chest resonance. These peaks increased as the subject moved aft of the aircraft. While the noise levels also increased, it was difficult to determine a relationship between acceleration and noise without additional data due to differences in the results between power settings. The subject did report an increased sensation of vibration in the upper torso, which coincided with the increased noise levels. These data will be used in the development of human airborne vibration exposure guidelines.

Criteria for developing active and passive isolation mechanisms for reducing the effects of whole-body vibration exposure rely on a thorough understanding of the stiffness, damping, and resonance behaviors of the human or human surrogate body. Three Rhesus monkeys were exposed to seated whole-body sinusoidal vibration between 3 and 20 Hz at 0.69 and 3.47 msec-2 rms (0.1 and 0.5 g peak) accelerations. The mechanical impedance magnitude and phase were calculated as the ratio and phase relation between the transmitted force and input velocity, respectively, at the seat. The resultant profiles showed a significant decrease in the primary resonance frequency with increasing acceleration. At the lower acceleration level, a second lower impedance peak was observed at approximately 5 Hz. A three-mass, two degree-of-freedom model, which included upper torso and leg representation, was used to determine the mechanical parameters that best described the measured responses. The mean stiffness coefficients and the mean undamped natural frequencies associated with the upper torso and leg subsystems showed a significant decrease with increases in the acceleration level. The results of this study strongly suggested that nonlinear stiffness properties were responsible for the observed differences in the biodynamic response of the Rhesus monkey with acceleration level.

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