[Analysis of intrauterine sounds and their tranquillizing effects on the newborn infant].

The authors have made a piezo-electric microphone in order to tap and analyse intrauterine sounds. The band that is used ranges from 3 - 700 Hz. A sound that has a small microphone at its tip is introduced into the uterus and then relayed to an amplifier. The sound mainly comes from the blood vessels and their frequency ranges between a few Hz and a thous and Hz. The acoustic pressure is big for low frequencies and weak for high frequencies. The sounds that are heard in the uterus have a calming effect on new-born children and stop them crying in 86% of cases where it has been tried. It sends them to sleep in 30% and this has been confirmed by E.E.G. This method is more effective than the older ones which used "slumber tone". The reason is that the product is the same as that which has been experienced by the fetus in utero.