Georg von Bekesy and the Place Theory of Pitch Perception

Excerpt from "Sound and Hearing", Stevens, S. S., & Warshofsky, Fred,eds., Time-Life Books, NY, 1965. p54

"The molder of the modern theory of basilar-membrane "resonance" is Georg von Bekesy. In 1928 Bekesy was a communications engineer in Budapest, studying the mechanical and electrical adaptation of telephone equipment to the demands of the human hearing mechanism. One day, in the course of a casual conversation, an acquantance asked him whether a major improvement would soon be forthcoming in the quality of telephone systems. The idle remark strarted a chain of thought that eventually posed to Bekesy a more fundamental question: "How much better is the quality of the human ear than that of any telephone system?" His search for the answer has added volumes to our present-day knowledge of hearing."

现代基膜‘共振’理论的奠基人是乔治·冯·贝克西。1928年，贝克西在布达佩斯担任通信工程师，研究电话设备如何适应人类听觉机制的需求。一天，在一次随意的谈话中，一位熟人问他是否很快电话系统的质量会有所重大改进。这个闲谈的 remark 引起了贝克西的一系列思考，最终提出了一个更根本的问题：‘人类耳朵的质量比任何电话系统更好吗？’他寻找答案的探索已为当今我们对听觉的理解增添了大量知识。

"Bekesy studied the inner ear by building mechanical models of the cochlea- e.g., a metal tube filled with water. Along the length of the tube ran a narrow slot covered by a stretched membrane, which served as the basilar membrane of the model. When the fluid was set in motion, he observed, it caused a bulge which swept like an undulating wave along the membrane. By adjusting the tension of the membrane along the slot he was able to confine the biggest part of the bulge to a particular region on the membrane. The undulation traveled down the length of the membane, but its amplitude - the bigness of the bulge- varied with position: the bulge was slight everywhere except in one area where it was large."

Bekesy通过构建耳蜗的机械模型来研究内耳——例如，一个装有水的金属管。在管子的长度方向上，有一个狭窄的槽，被一张拉伸的膜覆盖，这被用作模型的基底膜。当液体运动时，他观察到它导致膜上出现一个隆起，像波动的波一样沿膜传播。通过调整槽内膜的张力，他能够将最大的隆起部分限制在膜上的特定区域。波动沿膜的长度传播，但其振幅——即隆起的大小——随着位置变化：除了一个区域外，隆起都很小，而在那个区域则很大。

"He also detected the same wave movement in the cochlea itself. Using first animal ears and then the ears of human cadavers, he carefully cut out the cochlea and bored a tiny opening in the bone. Working under a microscope with "microtools" of his own invention (one pair of scissors had blades only a few thousandths of an inch long), he laid open part of the basilar membrane. The cochlear fluid was drained and replaced with a salt solution containing a suspension of powdered aluminum and coal. By scattering flashes of intense light off the powder suspension, Bekesy was able to follow events within the interior of the cochles. Under the microscope he saw a bulging undulation sweep over the basilar membrane when a sound was introduced into the cochlea. It was the same traveling wave he had seen coursing along the artificial membrane of his model."

他还在耳蜗本身中检测到了相同的波形运动。他首先使用动物耳，然后使用人体尸体的耳，仔细地取出耳蜗，并在骨头上钻出一个小孔。在显微镜下，他使用自己发明的‘微工具’（一对刀片只有几万分之一英寸长的剪刀），展开基底膜的一部分。耳蜗内的液体被排出并替换为含有铝粉和煤粉悬浮液的盐溶液。通过向悬浮的粉末散射强烈的光，贝克西能够追踪耳蜗内部的事件。在显微镜下，他看到当声音引入耳蜗时，基底膜上出现了一种隆起的波动。这正是他之前在人工膜上看到的 traveling wave。

"From this work Bekesy evolved his traveling-wave theory: a sound impulse sends a wave sweeping along the basilar membrane. As the wave moves along the membrane, its amplitude increases until it reaches a maximum, then falls off sharply until the wave dies out. That point at which the wave reaches its greatest amplitude is the point at which the frequency of the sound is detected by the ear. And as Helmholtz had postulated, Bekesy found that the high-frequency tones were perceived near the base of the cochlea and the lower frequencies toward the apex."

从这一‘功’中，贝克西发展出了他的行波理论：一个声波冲量会使一个波沿基底膜扫过。当波沿膜移动时，其振幅会增加直到达到最大值，然后迅速下降直到波消失。波达到最大振幅的那个点，正是声音频率被耳朵检测到的点。正如赫尔姆霍茨所提出的一样，贝克西发现高频声音被感知在耳蜗的基部，而低频声音则感知在顶部。

"No mammalian ear was beneath Bekesy's scrutiny. He observed the traveling wave in animals ranging from mouse to elephant. In the early 1940s he read that an elephant had died in the Budapest zoo. Immediately he went to the zoo to ask for the ears, but learned that the body had been sent to Budapest University. The University authorities reported that they had shipped the huge carcass to a glue factory. Finally, at the factory, he found the head still intact."

贝克西从未检查过哺乳动物的耳朵。他观察到从老鼠到大象的各种动物中的行波。20世纪40年代初，他读到一头大象在布达佩斯动物园死亡。他立刻前往动物园请求获取耳朵，但得知尸体已送往布达佩斯大学。大学当局报告说，他们已将这具庞大的尸体运送到一家胶水工厂。最后，在工厂里，他发现头仍然完好。

"That evening Bekesy sent his assistant to saw the portions of the skull containing the inner ears. The young man proudly returned with two large ears and chunks of bone. But when Bekesy peered into the ear canals, he found to his dismay that he could see clear through them; the prized inner ears were missing. Because an elephant's ear canal is about eight inches long, the assistant had not sawed in far enough. Bekesy sent him back to the glue factroy and this time he returned with the elephantine cochleas. To Bekesy's delight, the traveling wave phenomenon was clearly visible in the elephant."

那晚，贝克西派他的助手去切下含有内耳的头骨部分。年轻人自豪地带回了两个大耳和一些骨块。但当贝克西仔细观察耳道时，他惊恐地发现能清楚地看到里面；珍贵的内耳不见了。因为大象的耳道大约有八英寸长，助手并没有切到足够远。贝克西又让他去胶水工厂，这次他带回了象的耳蜗。贝克西高兴地发现，旅行波现象在象的耳蜗中清晰可见。

"For his studines of the traveling wave, Georg von Bekesy received the Nobel Prize in 1961. His incredible delicate and elegant experiments had traced sound to the very threshold of sensation. ..."

为了研究行波现象，乔治·冯·贝克西于1961年获得了诺贝尔奖。他非凡的精细而优雅的实验将声音追溯到了感觉的极阈。...