An analog electronic cochlea

An analog electronic cochlea has been built in CMOS VLSI technology using micropower techniques. The key point of the model and circuit is that a cascade of simple, nearly linear, second-order filter stages with controllable Q parameters suffices to capture the physics of the fluid-dynamic traveling-wave system in the cochlea, including the effects of adaptation and active gain involving the outer hair cells. Measurements on the test chip suggest that the circuit matches both the theory and observations from real cochleas

An Analog Electronic Cochlea

An engineered system that hears, such as a speech recognizer, can be designed by modeling the cochlea, or inner ear, and higher levels of the auditory nervous system. To be useful in such a system, a model of the cochlea should incorporate a variety of known effects, such as an asymmetric low-pass/bandpass response at each output channel, a short ringing time, and active adaptation to a wide range of input signal levels. An analog electronic cochlea has been built in CMOS VLSI technology using micropower techniques to achieve this goal of usefulness via realism. The key point of the model and circuit is that a cascade of simple, nearly linear, second-order filter stages with controllable Q parameters suffices to capture the physics of the fluid-dynamic traveling-wave system in the cochlea, including the effects of adaptation and active gain involving the outer hair cells. Measurements on the test chip suggest that the circuit matches both the theory and observations from real cochleas

A CMOS VLSI cochlea

An engineered system that hears, such as a speech recognizer, can be designed by modeling the cochlea, or inner ear, and higher levels of the auditory nervous system. To be useful in such a system, a model of the cochlea should incorporate a variety of known effects, such as an asymmetric lowpass/bandpass response at each output channel, a short ringing time, and active adaptation to a wide range of input signal levels. An analog electronic cochlea has been built in CMOS VLSI technology using micropower techniques to achieve this goal of usefulness via realism. The key point of the model and circuit is that a cascade of simple, nearly linear, second-order filter stages with controllable Q parameters suffices to capture the physics of the fluid-dynamic traveling-wave system in the cochlea, including the effects of adaptation and active gain involving the outer hair cells. Measurements on the test chip suggest that the circuit matches both the theory and observations from real cochleas

A Bidirectional Analog VLSI Cochlear Model

A novel circuit is presented for implementing a bidirectional passive cochlear model in analog VLSI. The circuit includes a subcircuit for modelling the fluid in the cochlear duct, and a subcircuit for modelling the passive basilar membrane. The circuit is compared to the classical 1-D transmission line cochlear model and found to be equivalent. The approach leads to an unexpected fa.ult tolerance in the form of insensitivity to transconductance amplifier offset voltages. A 545-stage cochlea has been fabricated and demonstrates the expected wave propagation behaviour

Refugees and national human rights institutions: A growing engagement

In recent years national human rights institutions have begun to bridge the long-standing gap between practice in the refugee and human rights fields. Often using their mandate as national preventive mechanisms under the Optional Protocol to the Convention Against Torture, NHRIs visit refugees in detention as well as in other types of camp. This has been particularly marked among Balkan ombudsman institutions in their response to the recent mass influx of refugees

Nonvolatile correction of Q-offsets and instabilities in cochlear filters

We present a feedback circuit that performs nonvolatile correction of instabilities and resonant-gain offsets (Q-offsets) in individual cochlear filters. The subthreshold CMOS circuit adapts using analog floating-gate technology. We present experimental data from a working chip that illustrates the performance of the circuit. We discuss how to extend our work to do very long-term gain control in the silicon cochlea. Positive-feedback circuits, such as our cochlear filters, are very sensitive to parameter variations. This potential problem becomes an advantage in our corrective feedback loop where the hypersensitivity behaves merely like high loop gain

An analog VLSI cochlea with new transconductance amplifiers and nonlinear gain control

We show data from a working 45-stage analog VLSI cochlea, built on a 2.2 mm×2.2 mm tiny chip. The novel architectural features in this cochlea are: (1) The use of a wide-linear-range low-noise subthreshold transconductance amplifier. (2) The use of “fuse-like” nonlinear positive-feedback amplification in the second-order cochlear filter. Several new circuit techniques used in the design are described here. The fuse nonlinearity shuts off the positive-feedback amplification at large signal levels instead of merely saturating it, like in prior designs, and leads to increased adaptation and improved large-signal stability in the filter. The fuse filter implements a functional model of gain control due to outer hair cells in the biological cochlea. We present data for travelling-wave patterns in our silicon cochlea that reproduce linear and nonlinear effects in the biological cochlea

Research Notes : Influence of maturity date on the oil content of soybeans with genetically altered fatty acid composition

sed oleic acid percentage has been proven successful in decreasing the percentage of linolenic acid in soybean oil (Burton et al., 1983). In the first four cycles of selection, the percentage of oleic acid in the seed oil increased linearly at an average rate of 1.6 + 0.2% per cycle whereas linoleic and linolenic acid percentages showed linear decreases. Four additional cycles of selection for increased oleic acid and two cycles for decreased oleic acid levels are currently being evaluated in a wide range of environ-ments

Effect of Rock Cover on Small Mammal Abundance in a Montana Grassland

We examined the influence of rock cover, as an indicator of presumable retreat site availability on the abundance of deer mice (Peromyscus maniculatus) and prevalence of Sin Nombre virus (SNV) using long-term live trapping and habitat data from three live trapping grids and a shortterm (three month), spatially replicated study across three slopes in Cascade County, Montana. In our long-term study, we found that deer mice were more abundant at a live-trapping grid with greater rock cover, than two grids with less rock cover. There was a non-significant trend (P = 0.053) for deer mice to be more abundant in rocky sites in the short term study. In the long-term study, average SNV antibody prevalence among deer mice was slightly greater (5.0 vs. 3.5 % on average) at the live trapping grid with more rock cover, than the grid with less rock cover. We were unable to demonstrate differences in SNV antibody prevalence among treatments in the short-term study. Further studies are needed to elucidate the multiple determinants of deer mouse abundance and SNV prevalence in grassland ecosystem and other habitat types

Improved implementation of the silicon cochlea

The original “analog electronic cochlea” of Lyon and Mead (1988) used a cascade of second-order filter sections in subthreshold analog VLSI to implement a low-power, real-time model of early auditory processing. Experience with many silicon-cochlea chips has allowed the identification of a number of important design issues, namely dynamic range, stability, device mismatch, and compactness. In this paper, the original design is discussed in light of these issues, and circuit and layout techniques are described which significantly improve its performance, robustness, and efficiency. Measurements from test chips verify the improved performance