Abstract: Surgical instruments, surgical techniques, grafts, cell and tissue isolation techniques, and a method for transplanting retinal cells, including photoreceptors, retinal pigment epithelium, and choroidea within their normal configuration, or all three tissues in a co-transplantation procedure are provided.

Abstract: An electronic filter for an electroacoustic system. The system has a microphone for generating an electrical output from external sounds and an electrically driven transducer for emitting sound. Some of the sound emitted by the transducer returns to the microphone means to add a feedback contribution to its electrical output. The electronic filter includes a first circuit for electronic processing of the electrical output of the microphone to produce a first signal. An adaptive filter, interconnected with the first circuit, performs electronic processing of the first signal to produce an adaptive output to the first circuit to substantially offset the feedback contribution in the electrical output of the microphone, and the adaptive filter includes means for adapting only in response to polarities of signals supplied to and from the first circuit.

Abstract: A noise reduction circuit for a hearing aid having an adaptive filter for producing a signal which estimates the noise components present in an input signal. The circuit includes a second filter for receiving the noise-estimating signal and modifying it as a function of a user's preference or as a function of an expected noise environment. The circuit also includes a gain control for adjusting the magnitude of the modified noise-estimating signal, thereby allowing for the adjustment of the magnitude of the circuit response. The circuit also includes a signal combiner for combining the input signal with the adjusted noise-estimating signal to produce a noise reduced output signal.

Abstract: A model simulating cochlear spectrum analysis is disclosed which includes a pair of matched all pole lattices interconnected by a plurality of tip couplers providing non-linear distributed bilateral signal processing. One of the lattices along with the tip couplers corresponds to the organ of Corti found in the cochlea and the second lattice corresponds to the basilar membrane also found in the cochlea such that the model provides a striking resemblance in structure to the physical properties of the cochlea itself. With the cochlea model disclosed, distortion products and otoacoustic emissions are simulated. An intermediate model is also disclosed which provides bilateral signal processing but lacks distributed amplification.

Abstract: An electronic filter for filtering an electrical signal. Signal processing circuitry therein includes a logarithmic filter having a series of filter stages with inputs and outputs in cascade and respective circuits associated with the filter stages for storing electrical representations of filter parameters. The filter stages include circuits for respectively adding the electrical representations of the filter parameters to the electrical signal to be filtered thereby producing a set of filter sum signals. At least one of the filter stages includes circuitry for producing a filter signal in substantially logarithmic form at its output by combining a filter sum signal for that filter stage with a signal from an output of another filter stage.

Abstract: An electronic filter for filtering an electrical signal. Signal processing circuitry therein includes a logarithmic filter having a series of filter stages with inputs and outputs in cascade and respective circuits associated with the filter stages for storing electrical representations of filter parameters. The filter stages include circuits for respectively adding the electrical representations of the filter parameters to the electrical signal to be filtered thereby producing a set of filter sum signals. At least one of the filter stages includes circuitry for producing a filter signal in substantially logarithmic form at its output by combining a filter sum signal for that filter stage with a signal from an output of another filter stage.

Abstract: An electronic filter for filtering an electrical signal. Signal processing circuitry therein includes a logarithmic filter having a series of filter stages with inputs and outputs in cascade and respective circuits asGOVERNMENT SUPPORTThis invention was made with U.S. Government support under Veterans Administration Contract VA KV 674P857 and National Aeronautics and Space Administration (NASA) Research Grant No. NAG10-0040. The U.S. Government has certain rights in this invention.

Abstract: An electronic filter for an electroacoustic system. The system has a microphone for generating an electrical output from external sounds and an electrically driven transducer for emitting sound. Some of the sound emitted by the transducer returns to the microphone means to add a feedback contribution to its electical output. The electronic filter includes a first circuit for electronic processing of the electrical output of the microphone to produce a filtered signal. An adaptive filter, interconnected with the first circuit, performs electronic processing of the filtered signal to produce an adaptive output to the first circuit to substantially offset the feedback contribution in the electrical output of the microphone, and the adaptive filter includes means for adapting only in response to polarities of signals supplied to and from the first circuit.

Abstract: Speech processing apparatus and methods utilizing a circuit for electronically deriving from speech over time a series of coordinate values representing positions of points on a path in a mathematical space which path positions represent the speech. An electronic memory prestores phonetic representations in correspondence with indicia of a glide in the path which indicia represent a nucleus in the space at which the glide begins and a range of directions of offglide on the path from the nucleus. A trajectory parameter is electronically computed from the series of coordinate values. When both the trajectory parameter satisfies a predetermined condition for significance and a coordinate value currently reached by the speech is within a predetermined region of such values, a signal is produced.

Abstract: Speech processing apparatus including a memory for holding prestored information indicative of different phonetic representations corresponding to respective sets of addresses in the memory. Circuitry in the apparatus electrically derives a series of coordinate values of points on a path in a mathematical space from frequency spectra of the speech occurring in successive time intervals respectively, identifies coordinate values approximating at least one position along the path of a peak in magnitude of acceleration, generates a memory address as a function of the position coordinate values and obtains from the memory the phonetic representation information prestored at that memory address. Methods and other apparatus for speech processing are also disclosed.

Abstract: Speech processing apparatus including an electronic memory and circuitry that derives from speech sets of digital values representative of frequency spectra. The spectra have peaks at frequencies associated therewith. The peaks include a highest magnitude peak for each spectrum. The circuitry also generates an auditory state signal representing the presence or absence of a burst-friction auditory state of the speech. Circuitry further electronically identifies, when the auditory state signal indicates the presence of a burst-friction auditory state, the highest magnitude peak for each spectrum as well as each peak having a magnitude within a range of magnitudes less than the magnitude of the highest magnitude peak, and selectively stores in distinct locations in the memory, respectively representative of normally occurring prominences of a burst-friction sound, the values of frequency of the lowest two frequencies associated with the identified peaks.

Abstract: A hearing aid including a microphone for generating an electrical output from sounds external to a user of the hearing aid, an electrically driven receiver for emitting sound into the ear of the user of the hearing aid, and circuitry for driving the receiver. The circuitry drives the receiver in a self-generating mode activated by a first set of signals supplied externally of the hearing aid to cause the receiver to emit sound having at least one parameter controlled by the first set of externally supplied signals and then drives the receiver in a filtering mode, activated by a second set of signals supplied externally of the hearing aid, with the output of the external microphone filtered according to filter parameters established by the second set of the externally supplied signals. Other forms of the hearing aid, apparatus for supplying the sets of signals to the hearing aid in a total system, and methods of operation are also described.