"The mind is a compact, multiply connected thought mass with internal connections of the most intimate kind. It grows continuously as new thought masses enter it, and this is the means by which it continues to develop."

Bernhard Riemann On Psychology and Metaphysics ca. 1860

"It is clear that the minds are the most important part of the universe, and that everything was established for their sake; that is, in choosing the order of things, the greatest account was taken of them; all things being arranged in such a way that they appear the more beautiful the more they are understood."

G. W. Leibniz

Today's Elites

Tuesday, April 19, 2011

Update on Model of Hearing

The researchers, Reichenbach and Hudspeth, that hypothesized a mechanism for sound amplification of the inner ear that I reported on in this blog from last September, have now put their theory in practice in design of a microphone that eliminates feedback and provides a capacity for tremendous sensitivity.

Unidirectional mechanical amplification as a design principle for an active microphone

Amplification underlies the operation of many biological and engineering systems. Simple electrical, optical, and mechanical amplifiers are reciprocal: the backward coupling of the output to the input equals the forward coupling of the input to the output. Unidirectional amplifiers that occur often in electrical and optical systems are special non-reciprocal devices in which the output does not couple back to the input even though the forward coupling persists. Here we propose a scheme for unidirectional mechanical amplification that we utilize to construct an active microphone. We show that amplification improves the microphone's threshold for detecting weak signals and that unidirectionality prevents distortion.

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