Spectral density estimation

About: Spectral density estimation is a research topic. Over the lifetime, 5391 publications have been published within this topic receiving 123105 citations.

Transform speech signal coding with pitch controlled adaptive quantizing

Abstract: To improve the speech quality at lower bit rates within a digital communication system in which the coefficients of a frequency transform (e.g. discrete cosine transform) are adaptively encoded with adaptive quantization and adaptive bit-assignment, the adaptation is controlled by a short-term spectral estimate signal formed by combining the formant spectrum and the pitch excitation spectrum of the coefficient signals.

Frequency analysis method

Abstract: A frequency analysis method comprises using a window function to evaluate aemporal input signal present in the form of discrete sampled values. The windowed input signal is subsequently subjected to Fourier transformation for the purpose of generating a set of coefficients. In order to develop such a method so that the characteristics of the human ear are simulated not only with respect to the spectral projection in the frequency range, but also with respect to the resolution in the temporal range, a set of different window functions is used to evaluate a block of the input signal in order to generate a set of blocks, weighted with the respective window functions, of sampled values whose Fourier transforms have different bandwidths, before each of the simultaneously generated blocks of sampled values is subjected to a dedicated Fourier transformation in such a way that for each window function at least respectively one coefficient is calculated which is assigned the bandwidth of the Fourier transforms of this window function, and that the coefficients are chosen such that the frequency bands assigned to them essentially adjoin one another.

Random sampling of evolution time space and Fourier transform processing.

Abstract: Application of Fourier Transform for processing 3D NMR spectra with random sampling of evolution time space is presented. The 2D FT is calculated for pairs of frequencies, instead of conventional sequence of one-dimensional transforms. Signal to noise ratios and linewidths for different random distributions were investigated by simulations and experiments. The experimental examples include 3D HNCA, HNCACB and (15)N-edited NOESY-HSQC spectra of (13)C (15)N labeled ubiquitin sample. Obtained results revealed general applicability of proposed method and the significant improvement of resolution in comparison with conventional spectra recorded in the same time.

Quantitative analysis of tremor time series.

Abstract: Spectral analysis is applied to tremor time series in basic research and treatment monitoring. The estimation of the spectra from the data is usually done by averaging the squared modulus of the Fourier transform of segments of the data. We discuss drawbacks of this method and propose an alternative procedure to estimate the spectra adaptively based on the data. Thus, the method can be applied to all types of tremor. Applying the theory of spectral estimation, we propose a method to decide whether a spectrum exhibits multiple significant peaks and discuss different approaches to determine the amplitude of the tremor from the spectrum.