但到了5世纪，罗马帝国崩塌了，中世纪开始了，香料直接贸易停止了，所以人们对于香料的运输和来源地的直接认识也就中断了。
But when Rome collapsed in the fifth century and the Middle Ages began, direct trade of spices stopped, and so did that kind of hands-on knowledge of travel and geography.
但我们必须认识到，增加杠杆导致危机的来源有两个。
But it is important to realize that the rise in leverage leading up to the crisis had two sources.
一项新的研究发现，有两个因素在发挥作用：一个是听众对于声音来源的认识，另一个是我们耳道那种令人遗憾的形状。
A new study finds that there are two factors at work: the knowledge of where the sound is coming from and the unfortunate design of our ear canals.
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