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Showing papers on "Cepstrum published in 1972"


Journal ArticleDOI
TL;DR: It is demonstrated that the simplified inverse filter tracking algorithm (hereafter referred to as the SIFT algorithm) encompasses the desirable properties of both autocorrelation and cepstral pitch analysis techniques.
Abstract: In this paper a new method for estimating F 0 , the fundamental frequency of voiced speech versus time, is presented. The algorithm is based upon a simplified version of a general technique for fundamental frequency extraction using digital inverse filtering. It is demonstrated that the simplified inverse filter tracking algorithm (hereafter referred to as the SIFT algorithm) encompasses the desirable properties of both autocorrelation and cepstral pitch analysis techniques. In addition, the SIFT algorithm is composed of only a relatively small number of elementary arithmetic operations. In machine language, SIFT should run in several times real time while with special-purpose hardware it could easily be realized in real time.

398 citations


Journal ArticleDOI
TL;DR: Digital data-processing problems such as the detection of multiple echoes, various methods of linear filtering the complex cepstrum, the picket-fence phenomenon, minimum-maximum phase situations, and amplitude- versus phase-smoothing for the additive-noise case are examined empirically and where possible theoretically, and are discussed.
Abstract: A technique for decomposing a composite signal of unknown multiple wavelets overlapping in time is described. The computation algorithm incorporates the power cepstrum and complex cepstrum techniques. It has been found that the power cepstrum is most efficient in recognizing wavelet arrival times and amplitudes while the complex cepstrum is invaluable in estimating the form of the basic wavelet and its echoes, even if the latter are distorted. Digital data-processing problems such as the detection of multiple echoes, various methods of linear filtering the complex cepstrum, the picket-fence phenomenon, minimum-maximum phase situations, and amplitude- versus phase-smoothing for the additive-noise case are examined empirically and where possible theoretically, and are discussed. A similar investigation is performed for some of the preceding problems when the echo or echoes are distorted versions of the wavelet, thereby giving some insight into the complex problem of separating a composite signal composed of several additive stochastic processes. The threshold results are still empirical and the results should be extended to multi-dimensional data. Applications are the decomposition or resolution of signals (e.g., echoes) in radar and sonar, seismology, speech, brain waves, and neuroelectric spike data. Examples of results are presented for decomposition in the absence and presence of noise for specified signals. Results are tendered for the decomposition of pulse-type data appropriate to many systems and for the decomposition of brain waves evoked by visual stimulation.

140 citations


Journal ArticleDOI
TL;DR: The algorithm discussed can achieve the decomposition of a certain class of noisy composite signals composed of nonidentical unknown multiple wavelets overlapping in time, namely those signals with reasonably well-defined independent resonances in the spectrum.
Abstract: Research in fields such as communication, speech, oceanography, seismic exploration, economics, and biomedical data processing is often directed toward the analysis of nonstationary or transient data. Complex demodulation is shown to be a valuable method that can be used to decompose a composite signal composed of differing transient wavelets and to estimate spectra. For the latter application it is shown that several other techniques recently advanced in the literature are special cases of complex demodulation. The algorithm discussed can achieve the decomposition of a certain class of noisy composite signals composed of nonidentical unknown multiple wavelets overlapping in time, namely those signals with reasonably well-defined independent resonances in the spectrum. The decomposition estimates the arrival time, peak, envelope, and frequency of the damped oscillatory transient wavelet. The procedure has been tested extensively and several selected experimental results are tendered. It has been found that for wavelets of the type t^{k}e^{-at} \sin (\omegat) , k =0, 1 , that an uncertainty relationship for the product of the 3-dB bandwidth and the time duration of the wavelet must be satisfied. An error analysis has established a relationship between envelope-and phase-estimation errors to wavelet and filter parameters. The results obtained via complex demodulation are discussed relative to those obtained via inverse filtering, the complex cepstrum, and the chirp z transform.

32 citations


Journal ArticleDOI
TL;DR: The technique of “cepstrum” analysis is shown to give a reliable indication of the firing rate even when the engine sound is deeply embedded in noise, in contrast to results obtained by some earlier workers using this analysis in speech studies.

23 citations


ReportDOI
30 Nov 1972
TL;DR: In this paper, an automatic spectral-fitting procedure based on a simple least-squares error criterion is devised for determining the source parameters of earthquakes from surface wave data, which is supplemented by the complex cepstrum technique for removing the spectral modulations due to multipath interference, results are significantly improved.
Abstract: : An automatic spectral-fitting procedure based on a simple least- squares error criterion is devised for determining the source parameters of earthquakes from surface wave data. When this procedure is supplemented by the complex cepstrum technique for removing the spectral modulations due to multipath interference, results are significantly improved. Rayleigh and Love wave spectral data recorded by the VLPE network and the NORSAR long-period array for fifty-one earthquakes in the Eurasian continent are processed by this procedure. The results are discussed on a regional basis. It is found that the surface wave spectral characteristics may vary even among earthquakes located in essentially the same epicentral region. However, the variations are not random but follow certain distinct patterns. With proper data coverage the focal depths of relatively small earthquakes can be estimated within a 20-km range by employing jointly the automatic spectral-fitting procedure and the complex cepstrum technique.

2 citations


Proceedings ArticleDOI
Chi-Hau Chen1
01 Jan 1972
TL;DR: In this article, the authors apply digital signal processing techniques to the marine seismic data to enhance the signal-to-noise ratio of the data and reconstruct the seismic profile from the digitally filtered data for better interpretation of the ocean bottom and the subbottom structure.
Abstract: The enormous amount of marine seismic data makes it necessary to process the data with a high speed digital computer. This paper is concerned with the application of digital signal processing techniques to the marine seismic data. The objectives of the study are two-fold: (1) to improve the data, i.e. to enhance the signal-to-noise ratio of the data and (2) to reconstruct the seismic profile from the digitally filtered data for a better interpretation of the ocean bottom and the subbottom structure. Cepstrum analysis, deconvolution, and Walsh domain processing of the data are discussed and the unpublished computer results are presented in detail.

2 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present results of both theoretical and experimental investigations on pitch extraction, showing that the observed periodicity is caused by the nonstationarity of the signal itself, and partly by the finite length of the time window of observation as well as its relative phase to the excitation signal.
Abstract: Recent techniques for pitch extraction are mostly based on detection of short‐time periodicity of certain time functions, such as autocorrelation function or cepstrum, derived by some transformations of the original speech signal. No systematic studies, however, have been made for the analysis and quantitative evaluation of the performance of these techniques. This paper presents results of both theoretical and experimental investigations on this problem. Deterioration in the observed periodicity is caused partly by the nonstationarity of the signal itself, and partly by the finite length of the time window of observation as well as its relative phase to the excitation signal. These effects are theoretically estimated for a given set of parameters of the speech signal and the analysis procedure, and lead to quantitative evaluation and comparison of various techniques thus far proposed. Results of the theoretical analysis are then confirmed and supplemented by experimental analysis of performances of these...

1 citations


Journal ArticleDOI
TL;DR: In this paper, a scheme has been developed that estimates five formant frequencies and amplitudes, along with intensity, zero-crossing, and slope change information, to make voiced-unvoiced decisions and to estimate the fundamental voicing frequency.
Abstract: The concept of a formant as representing a peak in the pressure spectrum is assumed to be applicable to both voiced and unvoiced speech. A scheme has been developed that estimates five formant frequencies and amplitudes. The cepstrum technique is used, along with intensity, zero‐crossing, and slope‐change information, to make voiced‐unvoiced decisions and to estimate the fundamental voicing frequency. An attempt is made to detect bursts of energy (due primarily to stop consonants) in the time waveform and to analyze them with sufficient time resolution so that the burst characteristic is preserved. The formant estimating procedure is based on assumed formant exclusive domains in frequency space. Several smoothing procedures are used to remove discontinuities from the formant and fundamental frequency data, and the smoothed values are used to control a five‐pole parallel synthesizer. The synthesizer is excited with a pulse train, noise, or a mixture of the two. Examples of the natural and synthetic speech are presented.

1 citations


Proceedings ArticleDOI
01 Aug 1972
TL;DR: Several digital processing techniques have been found to be of value in the computer analysis of the speech of deaf children as discussed by the authors, such as cepstrum analysis, chirp z transform, and predictive coding.
Abstract: Several digital processing techniques have been found to be of value in the computer analysis of the speech of deaf children. These techniques include the cepstrum analysis, chirp z transform, and predictive coding of the speech signal. The application of these techniques to the analysis of deaf speech, and the special problems that are encountered, are discussed. The accuracy of the speech parameter estimates obtained by these techniques is difficult to evaluate since the "true" values are not known. One approach to evaluating the accuracy of estimation is to synthesize the speech using the estimated parameter values. The computer simulation of the speech of deaf children has, thus far, shown a moderate degree of success. The computer synthesis of deaf speech also appears to be a diagnostic tool of great potential for the evaluation and treatment of speech problems.

1 citations