Georg von Békésy Biography (1899-1972)

physicist, physiologist

Georg von Békésy was a Hungarian-born scientist who discoveredhow sound is analyzed and communicated in the cochlea, part of the inner ear.For this work, in 1961 he became the first physicist to receive the Nobel Prize in medicine and physiology in 1961.

The son of a diplomat, Békésy was born in Budapest, Hungary. Hestudied at the University of Bern in Switzerland, graduating in 1920, and atthe University of Budapest, from which he received a doctorate in physics. He then worked at the Hungarian Telephone System Research Laboratory for nearly a quarter of a century. During this same period, he also worked at the central laboratories of Siemens and Halske AC in Berlin as well as serving on theUniversity of Budapest faculty. In 1946, after Soviet forces occupied Hungary, Békésy emigrated to Sweden, and then in 1947, to the UnitedStates. There he spent the next 23 years as a professor and researcher, firstat Harvard University (1949-1966) and then at the University of Hawaii (1966-1972).

It was Békésy's work as a telecommunications engineer for the Hungarian Telephone System that would prompt his research into the workings ofthe human ear. In order to determine what frequency range a cable would be able to carry, he decided to investigate how the human ear received sound. Hisresearch on the eardrum involved actually attaching two mirrors onto an eardrum and observing the reflections of the membrane's movements as sound wavesactivated it.

Békésy conducted another series of experiments in which he observed how parts of the middle ear, namely, the hammer, anvil, and stirrup, receive the vibrations transmitted by the eardrum and relay these messages to the cochlea in the inner ear. The fact that nerves in the cochlea pick up soundsignals and transmit them along the auditory nerve to the brain for interpretation had long been known. The importance of the basilar membrane, the vibratory tissue most critical for hearing, had also been well established. This membrane stretches the length of the snail-shaped cochlea, partitioning it into two canals, and contains groups of fine fibers, that widen as one moves along the cochlea to its tip.

A widely accepted theory at this time, put forth by Hermann von Helmholtz, held that each fiber on the basilar membrane had a natural period of vibrationand responded only to sounds that vibrated at that period. Each group of fibers was claimed to stimulate different nerve endings in this was enabling thebrain to differentiate specific frequencies.

Careful work by Békésy disproved the Helmholtz theory. He constructed models of cochlea and worked with cochlea from cadavers to test his ideas. By electrically stimulating the auditory mechanisms of his specimens, hewas able to study the function of the cochlea. Békésy had to develop new instruments and techniques for this delicate work. He designed extremely fine drills and probes, which were used to grind a small opening in the skull and then reach the basilar membrane. He used a saline solution containing fine aluminum particles to mimic the cochlea's natural fluid and was able to witness and measure for the first time a phenomenon he called the " traveling wave."

Békésy saw that the stirrup of the middle ear operated much like a lid on an opening in the cochlea, called the oval window. Sound vibrations cause the stirrup to move, exerting pressure on the fluid in the cochlea. The vibrations are transmitted to the basilar membrane in the form of traveling waves. Békésy found that the entire membrane vibrated. Each wave causes maximum vibration at different sections of the membrane accordingto its frequency. High-pitched sounds produce high-frequency waves that reachtheir peak on the part of the basilar membrane closest the stirrup, that is,near the cochlea's entrance. Low sounds produce low-frequency waves that reach their maximum amplitude farther along the membrane, near the end of the cochlea. Békésy discovered that pitch and loudness had to do withthe location and number of nerve receptors. The shape of the sound wave, along with the varying pitch, loudness, and quality, is what gives the brain theinformation to interpret.

Later, Békésy would also devise an audiometer to test hearing function and determine whether deafness had been caused by damage to the ear or to the brain, which facilitated proper treatment at an earlier stage.

In addition, Békésy became interested in visual and tactile sensations, which he measured and recorded. He developed a way for the skin to "hear," using equipment consisting of a much larger version of a cochlea. Whenits membrane was pressed against a person's skin, the skin could feel high and low sounds sent through the tube portion at distinctly different positionsalong the arm. Such experiments suggested new ways of helping the deaf and improved knowledge about deafness. Békésy passed away in 1972.

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