VLSI and Neural Net Systems (VNNS) Laboratory

Modeling the Cochlea

The mammalian cochlea performs a remarkable signal processing function that maps the frequency of the incoming signal into different spatial locations along its length. Researchers have long wanted to build an artificial device mimicking this frequency selectivity feature. However, fabricating and then sensing signals from such a small, typically hydro-mechanical structure is highly challenging. In this dissertation, we present the design of an artificial cochlea (ACochlea), together with the measured results and modeling studies to characterize and understand its performance. The measured results from this fluid-filled device demonstrate cochlear-like features.

This dissertation is composed of four major parts. Chapter 1 offers an explanation of the relevant physiology found in the mammalian cochlea, and also cites, with comments, prior work done to build and test an ACochlea. In Chapter 2, the general methods are introduced, including the construction of our ACochlea, the experimental setup and the computational model of the device. In Chapter 3, we present the measured and modeling results from the artificial basilar membrane (ABM), which is a critical sub-component of the ACochlea. Both the measured and modeling results show that the high tension on the ABM results in strong longitudinal coupling between beams. This coupling supports a traveling wave along the ABM surface, which degrades the ABM frequency response in air. In Chapter 4, the measured and modeling results on the ACochlea are presented. The measured results exhibit clear cochlear-like features: the slow traveling wave, the tonotopicity, and the sharp high frequency response cut-off. The computational model of the ACochlea is used to investigate the model sensitivity to its parameter values. The results indicate the methods required to improve the design of the ACochlea. Finally, the simulation results from the modified model demonstrate a frequency range of 100 Hz - 20 kHz. In Chapter 5, we summarize this thesis and propose the future work.

A hydro-mechanical cochlea was successful modeled, implemented and tested as a part of a Ph.D. thesis of Fangyi Chen. Figure 1a and Figure 1b show the developed devices.

Figure 2 shows the measurement result in comparison with the modeling result.

Figure 1a

Figure 1a

Figure 1b

Figure 1b

Figure 2

Figure 2

Last Modified: Sunday October 21, 2007