Baby In The Womb, What Do You Hear?

It has always been believed that unborn babies can hear but there were no clear indications when and how much they could hear. Researchers found that the fetus at 20 weeks had memory and perceptive capacity in the lower part of the brain, the thalamus. Scientists earlier had believed that, because the upper part of the brain -- the cortex -- did not develop until weeks later, the unborn child could not hear. In this study, researchers played music for unborn children at 20 weeks. Then they tested the response of babies two to three weeks after birth, and observed that their responses indicated they remembered the musical selections, and were soothed by replay.

More recently pegged by the US military concern that the noises emanating from their aircraft may affect unborn children a study was carried out using an ewe's womb. The acoustics of human and sheep wombs were inferred to be roughly the same.

To try to understand which sounds reach fetal ears, the researchers inserted a tiny electronic pick up into the fetus inner ear .For comparison, the researchers also placed a microphone inside the ewe's womb and another in the open air. The researchers recorded sentences from the open air, the ewe's womb, and the fetal sheep's inner ear and played them back randomly to 30 human listeners. It was found that 99% of the sentences recorded in the open air were understood, 73% for sentences recorded in the womb were intelligible and only 41% for those recorded in the fetal sheep's inner ear were understood. The inner ear recordings were inaudible because the high frequency consonants were found to be garbled.

This implies that fetuses can hear vowels with ease. Womb's walls soak up consonants, which are pronounced at higher frequencies, and the sound is muffled. Therefore mothers, who play music to their unborn children, should choose something with a lot of bass if they want their babies to hear the notes. An unborn baby is more likely to hear the drums than the violin and maybe the low notes on a piano.

The fact that the womb's walls filter most of the sound from outside will be a relief to expectant mothers who work in loud factories or attend rock concerts. The womb can be a very noisy place even in a quiet atmosphere as much of the noise that reaches a fetus is its mother's own voice, movement, breathing and digestive processes. Also, fetuses don't "hear" as much with their ears because their ears are filled with fluid, much noise is transmitted to their inner ears through vibrations in their skulls. As a result, the mother's voice tends to be the most dominant and recurring sound in the womb. While unborn children are insulated from many outer sound frequencies, premature children are exposed to all the frequencies of the sounds in the nursery. This finding also presents an interesting subject for researchers to find out how this added exposure, combined with the loss of the mother's voice, influences the development of these children.