It is commonly understood that ambient noise and sounds produced by a pregnant woman herself are propagated into the body and reach the unborn child in the uterus. However, it would be unethical to study the propagation of sound to the fetus directly, so the present study, which aimed to clarify this process from an acoustical point of view, used the stomach as a model of the womb. The following points were demonstrated: For sound waves in the stomach, no interference such as occurs outside the body was observed. However, in the range 2 to 3 kHz, a resonance peak was visible, which was probably due to the gastric air space. Observing an average spectrum of songs showed that the sound pressure level (SPL(dB)) in the medium to lower range (below 3 kHz) tended to be higher in the stomach than outside.
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