Identification of the impedance model of an implanted cochlear prosthesis from intracochlear potential measurements

Those suffering from a severe to profound sensorineural hearing loss can obtain substantial benefit from a cochlear implant prosthesis. An electrode array implanted in the inner ear stimulates auditory nerve fibers by direct injection of electrical current. A major limitation of today's technology is the imprecise control of intracochlear current flow, particularly the relatively wide spread of neural excitation. A better understanding of the intracochlear electrical fields is, therefore, required. This paper analyzes the structure of intracochlear potential measurements in relation to both the subject's anatomy and to the properties of the electrode array. An electrically equivalent network is proposed, composed of small lumped circuits for the interface impedance and for the cochlear tissues. The numerical methods required to estimate the model parameters from high-quality electrical potential recordings are developed. Finally, some models are presented for subjects wearing a Clarion CII device with a HiFocus electrode and discussed in terms of model reliability.     

Wavelet packet transform initialization for piecewise polynomialand bandlimited inputs

This paper considers the problem of initializing the wavelet packet transform when the analog input x(t) is either bandlimited or else is piecewise polynomial on the dyadic intervals. This is accomplished by the construction of certain prefilter sequences that are applied to the samples {x_k|x_k=x(kT)} (T is the sampling period). In the piecewise polynomial case, the prefilter sequences are computed with the aid of the interpolatory graphical display algorithm (IGDA), which is used to compute the so-called incremental moment functions of the scaling function φ(t) on the dyadic points. The moments of φ(t) are also employed     

Finite precision arithmetic and the split Schur algorithms

The split Schur algorithms of P. Delsarte and Y. Genin (1987) represent methods of computing reflection coefficients that are computationally more efficient, in terms of multiplications, than the conventional Schur algorithm by a constant factor. The authors investigate the use of fixed-point binary arithmetic, with quantization due to rounding, in the implementation of the symmetric and antisymmetric split Schur algorithms. It is shown, through a combination of analysis and simulation, that the errors in the reflection coefficient estimates due to quantization are large when the input signal is either a narrowband high-pass signal or a narrowband low-pass signal     

An algorithm for short-block data detection in the near-to-Toeplitzcase

Crozier et al. (1990, 1992) have developed schemes for estimating transmitted data on a block-by-block rather than symbol-by-symbol basis. In general, this requires the solution of a linear system of equations with a near-to-Toeplitz structure. In this paper, we apply the algorithm of Cybenko and Berry (1990) for the efficient solution of near-to-Toeplitz linear systems of equations to the data detection problem of Crozier et al. The algorithm of Cybenko and Berry is based upon the use of hyperbolic Householder transformations and is asymptotically more efficient in terms of the number of operations than a direct method of solution based, say, upon the use of a general Cholesky linear system solver. Because near-to-Toeplitz matrices can be very ill conditioned, even when the matrix is small, the application of Bischof's (1990) incremental condition estimator (ICE) algorithm is shown to be useful in detecting such ill conditioning     

QR-factorization method for computing the greatest common divisorof polynomials with inexact coefficients

This paper presents a novel means of computing the greatest common divisor (GCD) of two polynomials with real-valued coefficients that have been perturbed by noise. The method involves the QR-factorization of a near-to-Toeplitz matrix derived from the Sylvester matrix of the two polynomials. It turns out that the GCD to within a constant factor is contained in the last nonzero row of the upper triangular matrix R in the QR-factorization of the near-to-Toeplitz matrix. The QR-factorization is efficiently performed by an algorithm due to Chun et al. (1987). A condition number estimator due to Bischof (1990) and an algorithm for rank estimation due to Zarowski (1998) are employed to account for the effects of noise     

Schur algorithms for Hermitian Toeplitz, and Hankel matrices withsingular leading principal submatrices

It is shown how a simple matrix algebra procedure can be used to induce Schur-type algorithms for the solution of certain Toeplitz and Hankel linear systems of equations when given Levinson-Durbin algorithms for such problems. The algorithm of P. Delsarte et al. (1985) for Hermitian Toeplitz matrices in the singular case is used to induce a Schur algorithm for such matrices. An algorithm due to G. Heinig and K. Rost (1984) for Hankel matrices in the singular case is used to induce a Schur algorithm for such matrices. The Berlekamp-Massey algorithm is viewed as a kind of Levinson-Durbin algorithm and so is used to induce a Schur algorithm for the minimal partial realization problem. The Schur algorithm for Hermitian Toeplitz matrices in the singular case is shown to be amenable to implementation on a linearly connected parallel processor array of the sort considered by Kung and Hu (1983), and in fact generalizes their result to the singular case