Current LPC synthesizers have a problem when the driving function is periodic; an output synthesized from LPC analysis has spectral properties which are not identical to those of the analyzed input. These distortions ...
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Current LPC synthesizers have a problem when the driving function is periodic; an output synthesized from LPC analysis has spectral properties which are not identical to those of the analyzed input. These distortions prevent a vocoder from being truly transparent for many voiced sounds. An iterative method, which modifies the conventional LPC coefficients such that the autocorrelation function of the output becomes identical to that of the input, is presented. A methodology for keeping the increased computational cost to a minimum is also to be discussed.
Present plans for a defense communications digital voice network require both 16 kbit/s delta modulation (DM) and 2.4 kbit/s linear predictive coding (LPC). Unfortunately, when the output of a delta modulator receiver...
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Present plans for a defense communications digital voice network require both 16 kbit/s delta modulation (DM) and 2.4 kbit/s linear predictive coding (LPC). Unfortunately, when the output of a delta modulator receiver is used as the input to an LPC system, the speech synthesized by the LPC receiver is noticeably degraded. This paper investigates the use of sequential estimation algorithms to reduce this degradation without changing the given DM and LPC system designs. It is found that a particular scalar sequential filtering structure reduces the Itakura spectral distance measure by 60 percent, provides a more accurate LPC output spectrum, and provides a definite perceptual improvement in output speech quality. Most of the improvement is at higher frequencies, however.
The purpose of this work was to study, experimentally, two windowless LPC analysis algorithms for use in speech digitization. The two algorithms are a circular autocorrelation technique which utilizes the pseudoperiod...
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The purpose of this work was to study, experimentally, two windowless LPC analysis algorithms for use in speech digitization. The two algorithms are a circular autocorrelation technique which utilizes the pseudoperiodic nature of voiced speed, and a reflection coefficient estimation technique suggestion by J. P. Burg. Both techniques showed considerable promise in the experimental results.
The architectures of two medium-sized digital telephone switching systems that were developed in China, the DS-30 and HJD-04 systems, are discussed. The DS-30 is a 30000 line digital telephone switching system, with a...
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The architectures of two medium-sized digital telephone switching systems that were developed in China, the DS-30 and HJD-04 systems, are discussed. The DS-30 is a 30000 line digital telephone switching system, with a total capacity of 300000 busy hour call attempts (BHCA) using digital line concentration and a time-space-time switch fabric. Its architecture is a distributed control, multistage, multiprocessor system with load and function sharing. The HJD-04 is a 30000 line digital telephone switching system, with a total capacity of 2 million BHCA. The significant feature of the HJD-04 system is its switching network, which consists of a single time switch. The structure of the switching software support environment used in China is discussed.< >
In this work, accurate spectral envelope estimation is applied to Voice Conversion in order to achieve High-Quality timbre conversion. True-Envelope based estimators allow model order selection leading to an adaptatio...
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ISBN:
(纸本)9781424423538
In this work, accurate spectral envelope estimation is applied to Voice Conversion in order to achieve High-Quality timbre conversion. True-Envelope based estimators allow model order selection leading to an adaptation of the spectral features to the characteristics of the speaker. Optimal residual signals can also be computed following a local adaptation of the model order in terms of the F-0. A new perceptual criteria is proposed to measure the impact of the spectral conversion error. The proposed envelope models show improved spectral conversion performance as well as increased converted-speech quality when compared to linear Prediction.
We applied and compared two supervised pattern recognition techniques, namely the Multilayer Perceptron (MLP) and Support Vector Machine (SVM), to classify seismic signals recorded on Stromboli volcano. The available ...
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ISBN:
(纸本)9781607500728
We applied and compared two supervised pattern recognition techniques, namely the Multilayer Perceptron (MLP) and Support Vector Machine (SVM), to classify seismic signals recorded on Stromboli volcano. The available data are firstly preprocessed in order to obtain a compact representation of the raw seismic signals. We extract from data spectral and temporal information so that each input vector is made up of 71 components, containing both spectral and temporal information extracted from the early signal. We implemented two classification strategies to discriminate three different seismic events: landslide, explosion-quake, and volcanic microtremor signals. The first method is a two-layer MLP network, with a Cross-Entropy error function and logistic activation function for the output units. The second method is a Support Vector Machine, whose multi-class setting is accomplished through a 1vsAll architecture with gaussian kernel. The experiments show that although the MLP produces very good results, the SVM accuracy is always higher, both in term of best performance, 99.5%, and average performance, 98.8%, obtained with different sampling permutations of training and test sets.
In the last several years, a wide variety of techniques have been developed which make practical the implementation and development of large networks for recognizing connected sequences of words. Included among these ...
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In the last several years, a wide variety of techniques have been developed which make practical the implementation and development of large networks for recognizing connected sequences of words. Included among these techniques are efficient and accurate speech modeling methods (e.g., vector quantization, hidden Markov models) and efficient, optimal network search procedures (i.e., level building). In this paper we show how to integrate these techniques to give a speaker-independent, syntax-directed, connected word recognition system which requires only a modest amount of computation, and whose performance is comparable to that of previous recognizers requiring an order of magnitude more computation. In particular, the recognizer we studied was an airlines information and reservation system using a 129 word vocabulary, and a deterministic syntax (grammar) with 144 states, 450 state transitions, and 21 final states, generating more than 6 × 10 9 sentences. An evaluation of the system, using six talkers each speaking 51 test sentences, yielded a sentence accuracy of about 75 percent resulting from a word accuracy of about 93 percent, for an average speaking rate of about 210 words per minute.
High quality speech at low bit rates (e.g., 2400 bits/s) is one of the important objectives of current speech research. As part of long range activity on this problem, we have developed an efficient computer program t...
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High quality speech at low bit rates (e.g., 2400 bits/s) is one of the important objectives of current speech research. As part of long range activity on this problem, we have developed an efficient computer program that will serve as a tool for investigating whether articulatory speech synthesis may achieve this low bit rate. At a sampling frequency of 8 kHz, the most comprehensive version of the program, including nasality and frication, runs at about twice real time on a Cray-1 computer.
The nature of some high-value systems requires that damage be detected without disassembly of the test article. Spin-down testing, one such nondestructive evaluation method, involves spinning a test article and observ...
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ISBN:
(纸本)9783319300849;9783319300832
The nature of some high-value systems requires that damage be detected without disassembly of the test article. Spin-down testing, one such nondestructive evaluation method, involves spinning a test article and observing its angular deceleration. An increase in angular deceleration compared to an identical test of a healthy system indicates damage has occurred. However, current testing is limited, providing only a binary result of "damaged" or "undamaged". More sophisticated techniques are required to identify the location, extent, and type of damage. To achieve this, non-contact and surface-mounted sensors were used to monitor the test article in this experiment. A spin-down unit was used to test both a healthy specimen and a specimen with simulated damage. The signals from each sensor were compared across tests. Correlation of anomalous signals with rotational position and multi-sensor triangulation techniques were used to localize damage. Analysis of the frequency content and amplitude of output signals allowed for a degree of characterization of the damage. Through these techniques, spin-down testing was enhanced from a binary detector to a more thorough testing method giving detailed information about the type and location of damage.
A study of the autocorrelation LPC analysis of speech in additive noise is presented. In the noise-free case it is shown that finite word length implementation of the analysis may produce stable but poor spectral esti...
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A study of the autocorrelation LPC analysis of speech in additive noise is presented. In the noise-free case it is shown that finite word length implementation of the analysis may produce stable but poor spectral estimates. The beneficial effects of proper preemphasis are reaffirmed in terms of decreased numerical error as well as decreased LPC order needed for a good spectral fit. For the ease of noisy input speech the conditions for severe distortion of the spectral estimate are presented. A proper LPC spectral analysis of speech in additive noise is shown to require a higher order fit than currently used, a more precise implementation, and a more accurate parameter quantization for transmission.
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