拔智齿后牙齿酸痛:子宫日记（12）

In the womb 12

At 3 months old the fetus’s most developed sense is hearing. The fetus may be completely surrounded by amniotic fluid, but because sound travels through fluid about four times faster than it does in air, she has plenty to hear. The first sounds the fetus hears as her ears start picking up vibrations at 13 weeks are the gurgles(咯咯声) and rumbles(辘辘声) made by her mother’s body. A succession of hiccups(打嗝), burps(打饱嗝), bubbles(泡泡), sloshes(溅泼声) and slurps(啧啧) marks the passage of food, liquid and air in, out and through the maze(迷宫) of passages and tubes just inches(缓缓进入) from the baby’s ears.

三个月的时候胎儿发育得最好的感觉是听力。胎儿被羊水完全包裹着，但是因为声音在液体中传送的速度比在空气中快四倍，所以孩子能听到很多声音。胎儿的耳朵在13周有活力后，听到的第一种声音是母亲身体发出的咯咯咕咕声。食物、液体、空气进出母亲身体中迷宫一般的管道时发出的一系列的声音，如打嗝、冒泡、啧啧吃的声音都会缓慢进入孩子的耳朵。

The fetus also makes her own noises as she kicks and swishes(嗖嗖地挥动) in the amniotic fluid. She can also hear the competing flutter of heartbeats, her own racing at twice the speed of her mother’s, both her constant companions during her time in the womb. The fetus can also hear sounds from the world outside: conversations, loud noises and music. The walls of the womb, together with the abdomen, act to filter out most of the high frequencies. All sounds reach the fetus distorted, but higher sounds are more muffled(蒙). Only the lower-bass(低音) notes of a piece of music have much impact.

胎儿本身也会发出很多声音，因为她一直在羊水里踢脚扭动。她能听见两种心跳竞相跳动的声音，母亲的心跳和自己比母亲快两倍的心跳，两种心跳声会一直陪伴她过完子宫中的时光。胎儿也能听到来自外面世界的声音：谈话声、噪音和音乐。子宫壁和母亲肚子滤掉了大部分高频率的声音。胎儿听到的所有声音都已经被改变，声音越高听起来就越闷闷的。只有某些音乐中的低音听起来才更完整。

Voice’s sound is distorted too. Vowels(元音) are generally lower in pitch than consonants(辅音), so the fetus only hear the melody of speech without the percussion(打击) of consonants. The sound of the mother’s voice is different from any other since it travels directly through the fluids of the body. This may help the baby develop the unique relationship it has with its mother.

人说话的声音也被改变了。元音通常比辅音更低，所以胎儿只能听到没有辅音的说话声。母亲的声音与其它声音都不一样，因为是直接通过身体里的液体传送。这也许能帮助建立起孩子与母亲之间独一无二的亲情。

Other voices like the father’s must pass through air, then fluid and may not cut through the general background noise. The loudest sound of a fetus will ever hear may come during an ultrasound scan. It’s impossible to hear the actual ultrasound waves. They are far too high at frequency to affect the human ear, but the ultrasound can cause secondary waves in the amniotic fluid that the baby can hear.

 其他人的声音比如父亲的声音一定要通过空气、再通过液体传送，所以可能无法从环境中的其他声音区分出来。胎儿听到的最响的声音可能是做超声波检查时的声音。胎儿不可能听到真正的超声波声音，因为这些声波频率太高，人耳听不到。但是超声波会引起羊水的二次波动，胎儿就能听到。

To produce finely-detailed images, ultrasound probes fire a rapid succession of pulses(脉冲), each lasting less than one millionth of a second. The rapid switching on-and-off of these pulses can cause waves in the fluid which sound like a high-pitch tapping. If the probe is pointed directly at the baby’s ear, it can sound as loud as a subway train.

为了获得精致的图像，超声波检查时会发出一系列高速脉冲，每一次持续不超过百万分之一秒。脉冲的变化会引起羊水波动，听起来就像很响的叩击声。如果探测器刚好插到孩子的耳朵旁，造成的声音听起来就像一列地铁开过。

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