Three Dimensional Sound and Vibration Frequency Responses of the Sheep Abdomen

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Abstract
There is growing awareness and concern about reproductive hazards in the workplace. Sound and vibration have long been recognized as occupational hazards, but there are no guidelines or consensus standards for foetal protection. A three-dimensional analysis of sound pressure level (SPL) within the abdomen was used to show how sound and vibration of various frequencies are transmitted throughout the abdominal segment of sheep. Sinusoidal stimulation was provided with a mechanical vibrator placed on the anterior abdominal wall just posterior to the umbilicus. A hydrophone was placed at 45 intraabdominal locations within a space measuring 20×20×25 cm centered over the mechanical oscillator. Pure tones of 10, 100, 1000 and 2000 hertz were used to stimulate the abdominal wall. Intraabdominal SPL was negatively correlated with distance between the hydrophone and the vibrator (p<0.0001) and was negatively correlated with frequency of vibration (p<0.0001). The rate at which the system attenuated high frequencies was greater than for lower frequencies and it attenuated higher frequencies more uniformly throughout the entire abdomen (p<0.0001).

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