Contemporary applications of natural and synthetic zeolites from fly ash in agriculture and environmental protection

Trunk injection of plant protection products to protect trees from pests and diseases

With the progress of speech synthesis towards the development of complete TTS systems, the databases of speech synthesizers obtain more and more similarity with databases of speech recognizers. This offers new possibilities in combining systems for speech synthesis and recognition. In a new project, we are developing a speech dialogue system with the synthesis and recognition components using unified databases. In this paper, we describe the aim of the project, the framework of the system and first results at the acoustic and the word level.

A unified approach for speech synthesis and speech recognition using stochastic Markov graphs.

In recent years, increasing the midsole bending stiffness (MBS) of running shoes by embedding carbon fibre plates in the midsole resulted in many world records set during long-distance running competitions. Although several theories were introduced to unravel the mechanisms behind these performance benefits, no definitive explanation was provided so far. This study aimed to investigate how the function of the gastrocnemius medialis (GM) muscle and Achilles tendon is altered when running in shoes with increased MBS. Here, we provide the first direct evidence that the amount and velocity of GM muscle fascicle shortening is reduced when running with increased MBS. Compared to control, running in the stiffest condition at 90% of speed at lactate threshold resulted in less muscle fascicle shortening (p = 0.006, d = 0.87), slower average shortening velocity (p = 0.002, d = 0.93) and greater estimated Achilles tendon energy return (p ≤ 0.001, d = 0.96), without a significant change in GM fascicle work (p = 0.335, d = 0.40) or GM energy cost (p = 0.569, d = 0.30). The findings of this study suggest that running in stiff shoes allows the ankle plantarflexor muscle-tendon unit to continue to operate on a more favourable position of the muscle's force-length-velocity relationship by lowering muscle shortening velocity and increasing tendon energy return.

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Increasing the midsole bending stiffness of shoes alters gastrocnemius medialis muscle function during running.

The Drift-Diffusion Model (DDM) is the prevalent computational model of the speed-accuracy trade-off in decision making. The DDM provides an explanation of behavior by optimally balancing reaction times and error rates. However, when applied to value-based decision making, the DDM makes the stark prediction that reaction times depend only on the relative utility difference between the options and not on absolute utility magnitudes. This prediction runs counter to evidence that reaction times decrease with higher utility magnitude. Here, we ask if and how it could be optimal for reaction times to show this observed pattern. We study an algorithmic framework that balances the cost of delaying rewards against the utility of obtained rewards. We find that the functional form of the cost of delay plays a key role, with the empirically observed pattern becoming optimal under multiplicative discounting. We add to the empirical literature by testing whether utility magnitude affects reaction times using a novel methodology that does not rely on functional form assumptions for the subjects’ utilities. Our results advance the understanding of how and why reaction times are sensitive to the magnitude of rewards.

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Sensitivity of reaction time to the magnitude of rewards reveals the cost-structure of time.

Recently, 3D printing has been increasingly used to create physical models of the vocal tract with geometries obtained from magnetic resonance imaging. These printed models allow measuring the vocal tract transfer function, which is not reliably possible in vivo for the vocal tract of living humans. The transfer functions enable the detailed examination of the acoustic effects of specific articulatory strategies in speaking and singing, and the validation of acoustic plane-wave models for realistic vocal tract geometries in articulatory speech synthesis. To measure the acoustic transfer function of 3D-printed models, two techniques have been described: (1) excitation of the models with a broadband sound source at the glottis and measurement of the sound pressure radiated from the lips, and (2) excitation of the models with an external source in front of the lips and measurement of the sound pressure inside the models at the glottal end. The former method is more frequently used and more intuitive due to its similarity to speech production. However, the latter method avoids the intricate problem of constructing a suitable broadband glottal source and is therefore more effective. It has been shown to yield a transfer function similar, but not exactly equal to the volume velocity transfer function between the glottis and the lips, which is usually used to characterize vocal tract acoustics. Here, we revisit this method and show both, theoretically and experimentally, how it can be extended to yield the precise volume velocity transfer function of the vocal tract.

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How to precisely measure the volume velocity transfer function of physical vocal tract models by external excitation

A detailed understanding of how the acoustic patterns of speech sounds are generated by the complex 3D shapes of the vocal tract is a major goal in speech research. The Dresden Vocal Tract Dataset (DVTD) presented here contains geometric and (aero)acoustic data of the vocal tract of 22 German speech sounds (16 vowels, 5 fricatives, 1 lateral), each from one male and one female speaker. The data include the 3D Magnetic Resonance Imaging data of the vocal tracts, the corresponding 3D-printable and finite-element models, and their simulated and measured acoustic and aerodynamic properties. The dataset was evaluated in terms of the plausibility and the similarity of the resonance frequencies determined by the acoustic simulations and measurements, and in terms of the human identification rate of the vowels and fricatives synthesized by the artificially excited 3D-printed vocal tract models. According to both the acoustic and perceptual metrics, most models are accurate representations of the intended speech sounds and can be readily used for research and education. Machine-accessible metadata file describing the reported data: https://doi.org/10.6084/m9.figshare.12591554

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Printable 3D vocal tract shapes from MRI data and their acoustic and aerodynamic properties.

The estimation of formant frequencies from acoustic speech signals is mostly based on Linear Predictive Coding (LPC) algorithms. Since LPC is based on the source-filter model of speech production, the formant frequencies obtained are often implicitly regarded as those for an infinite glottal impedance, i.e., a closed glottis. However, previous studies have indicated that LPC-based formant estimates of vowels generated with a realistically varying glottal area may substantially differ from the resonances of the vocal tract with a closed glottis. In the present study, the deviation between closed-glottis resonances and LPC-estimated formants during phonation with different peak glottal areas has been systematically examined both using physical vocal tract models excited with a self-oscillating rubber model of the vocal folds, and by computer simulations of interacting source and filter models. Ten vocal tract resonators representing different vowels have been analyzed. The results showed that F1 increased with the peak area of the time-varying glottis, while F2 and F3 were not systematically affected. The effect of the peak glottal area on F1 was strongest for close-mid to close vowels, and more moderate for mid to open vowels.

How the peak glottal area affects linear predictive coding-based formant estimates of vowels

We are presenting an interactive course on speech synthesis which is designed to support the education in speech communication. In the basic section, the fundamental principles of speech synthesis are explained. To explore a complete text-to-speech (TTS) system, the user is provided with access to the Dresden Speech Synthesizer DreSS. The user may type any text, and he may observe how the system processes the text from the first linguistic preprocessing until the acoustic synthesis. A further section is devoted to the crucial problem of correct segmentation of the speech elements used for the concatenative synthesis. The user may select his own diphone segments from a given speech data base. The quality of the segments may be evaluated acoustically, and hints are given to avoid errors in cutting. Thus, the user will learn how to select the segments with good quality. The course is written in HTML and Java and is designed for Internet application.

An interactive tutorial on text-to-speech synthesis from diphones in time domain.

Physical models of the vocal tract need a suitable voice source to generate vocalic sounds. Here we constructed and tested three types of voice sources:a self-oscillating silicone model of the vocal folds, a vibrating reed source, and asource based on an electro-mechanical loudspeaker. Each of the sources was usedto excite eight physical resonators representing the German tense vowels. The excitation signals generated by the sources were analyzed and the intelligibility of thegenerated vowel sounds was perceptually evaluated. The spectral slope of the excitation was steepest for the silicone vocal folds, least steep for the reed source, andin-between for the loudspeaker source. The intelligibility of the vowels was highest for the excitation with the silicone vocal folds, and lowest for the loudspeakersource.

Steffen Kürbis

Papers

How to precisely measure the volume velocity transfer function of physical vocal tract models by external excitation

Printable 3D vocal tract shapes from MRI data and their acoustic and aerodynamic properties.

How the peak glottal area affects linear predictive coding-based formant estimates of vowels

An interactive tutorial on text-to-speech synthesis from diphones in time domain.

Comparison of different methods for the voiced excitation of physical vocal tract models