Fetal vibroacoustic stimulation test: vibrator response characteristics in pregnant sheep postmortem.

Objective: To determine the effect of small decreases in battery voltage on tHe sound pressure level and spectral features of sound within the uterus dig vibroacoustic stimulation with a battery-powered electronic artificial larynx. Methods: In eight pregnant, recently sacrificed sheep, the fluid-borne, intra-amniotic sound pressures resulting from vibration of the abdominal wall with an electronic artificial larynx were compared with airbome sound pressures produced by an artificial larynx and measured at 50 cm. Results: At all frequencies, the intrauterine sound pressure was higher than the sound pressure in air