A life-sized physical model of the human cochlea with optical holographic readout

Abstract

A life-sized physical model of the human cochlea is demonstrated. The model consists of two fluid-filled chambers separated by a polymer membrane and connected through a small hole that serves the same functional purpose as the helicotrema. The dimensions of the two chambers were made identical to those of scala vestibuli and scala tympani in the real cochlea. The membrane's width and length are the same as the values measured for the biological basilar membranes, and its thickness is chosen to give it appropriate rigidity. A piezoelectric transducer drives the system via an elastic window (acting as the oval window) on one side of the scala vestibuli. The resulting vibration pattern on the basilar membrane is investigated with an optical novelty filter, with detection sensitivity of 0.3 A at 2 kHz with a 1-Hz bandwidth. The overall response of this model is found to be a good extrapolation of Bekesy's low-frequency data. However, the tuning curves of this model are not as sharp as those found by Rhode, Johnstone, and others from the in vivo measurements. Possible implications of these results are discussed.

Toward Three-Dimensional Analysis of Cochlear Structure

“…However, a viscosity of the fluid 28 times that of saline was used for optical purposes, and the exact thickness of the basilar membrane is not given. Our computations for this case with a reasonable taper in the basilar membrane thickness are in rea- [37] (dashed curves) for the amplitude envelopes for different frequencies. This is a life-size model, but with an isotropic BM and fluid viscosity 28 times that of water.…”

“…Helle measured all fluid and basilar membrane viscoelastic properties, so there were no free parameters for 'adjusting' results. The recent experimental model by Zhou et al [37] is valuable since it is the first life-sized physical experimental model and therefore requires no scaling. However, a viscosity of the fluid 28 times that of saline was used for optical purposes, and the exact thickness of the basilar membrane is not given.…”

Experimental and Analytical Study Approach of Artificial Basilar Membrane Prototype (ABMP)

“…Steele & Taber analyzed and constructed a mechanical cochlear model using a three odel. Zhou, et al [3] used an isotropic polymer membrane placed…”

Fully Micromachined Lifesize Cochlear Model

“…Laser Doppler Velocimetry (LDV) measurements show cochlear-like traveling fluid structure waves with a phase lag of approximately 3 cycles (6π radians) and displacement magnitude of 0.2-0.5 nm/Pa at the location of maximum response. The device responds in the 10-70 kHz band.To date, three groups have reported the construction of life-sized physical cochlear models [1,2,3]. These systems use a polymer membrane on a micromachined support as the "basilar membrane" (BM), and use casting, milling, or small-scale electro-discharge machining (EDM) to create two fluid ducts on either side of the membrane.…”

“…To date, three groups have reported the construction of life-sized physical cochlear models [1,2,3]. These systems use a polymer membrane on a micromachined support as the "basilar membrane" (BM), and use casting, milling, or small-scale electro-discharge machining (EDM) to create two fluid ducts on either side of the membrane.…”