An extended two-dimensional vocal tract model for fast acoustic simulation of single-axis symmetric three-dimensional tubes

The simulation of two-dimensional (2D) wave propagation is an affordable computational task and its use can potentially improve time performance in vocal tracts' acoustic analysis. Several models have been designed that rely on 2D wave solvers and include 2D representations of three-dimensional (3D) vocal tract-like geometries. However, until now, only the acoustics of straight 3D tubes with circular cross-sections have been successfully replicated with this approach. Furthermore, the simulation of the resulting 2D shapes requires extremely high spatio-temporal resolutions, dramatically reducing the speed boost deriving from the usage of a 2D wave solver. In this paper, we introduce an in-progress novel vocal tract model that extends the 2D Finite-Difference Time-Domain wave solver (2.5D FDTD) by adding tube depth, derived from the area functions, to the acoustic solver. The model combines the speed of a light 2D numerical scheme with the ability to natively simulate 3D tubes that are symmetric in one dimension, hence relaxing previous resolution requirements. An implementation of the 2.5D FDTD is presented, along with evaluation of its performance in the case of static vowel modeling. The paper discusses the current features and limits of the approach, and the potential impact on computational acoustics applications.Comment: 5 pages, 2 figures, Interspeech 2019 submissio

Talking tube : a novel approach for vocal tract acoustic modelling using the finite-difference time-domain method

The human voice is a complex but unique physiological process. It involves the neuromuscular control of articulators to form an intricate upper vocal tract geometry, which yields different speech sounds. The existing computational vocal tract models have significant limitations concerning acoustic precision and simulation performance. The high-dimensional vocal tract models can compute precise acoustic wave propagation at the expense of simulation run-time. This thesis aims to fill these lacunae through two major contributions. Firstly, we introduce a novel vocal tract that extends the existing two-dimensional (2D) vocal tract modelling approach while having three-dimensional behaviour. The proposed model (2.5D FDTD) employs the Finite-Difference Time-Domain numerical scheme to discretize and compute acoustic components on a staggered grid. The simulated acoustic outputs of our new model are shown to match with the 2D FDTD vocal tract model at a low spatiotemporal resolution for open static vocal tract shapes. Contrary to 2D FDTD, the model adds tube depth as an additional impedance parameter to the acoustic wave solver by lumping off-plane waves. This technique offers an excellent balance between computational cost and acoustic precision while promising better geometrical flexibility for vocal tract modelling. Secondly, we tested the model's basic capabilities through the acoustic simulation of cardinal English vowel sounds. For realistic modelling of vowel sounds, we built a vocal tract radiation model. We also couple the 2.5D vocal tract with a self-oscillatory lumped-element vocal fold model to illustrate a fully connected articulatory speech synthesizer. This study offers a speech synthesis tool that can generate static vowel sounds and set up a new pathway for lightweight vocal tract modelling and other computational acoustic research.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field