14,198 research outputs found
Feasibility of reduced gravity experiments involving quiescent, uniform particle cloud combustion
The study of combustible particle clouds is of fundamental scientific interest as well as a practical concern. The principal scientific interests are the characteristic combustion properties, especially flame structure, propagation rates, stability limits, and the effects of stoichiometry, particle type, transport phenomena, and nonadiabatic processes on these properties. The feasibility tests for the particle cloud combustion experiment (PCCE) were performed in reduced gravity in the following stages: (1) fuel particles were mixed into cloud form inside a flammability tube; (2) when the concentration of particles in the cloud was sufficiently uniform, the particle motion was allowed to decay toward quiescence; (3) an igniter was energized which both opened one end of the tube and ignited the suspended particle cloud; and (4) the flame proceeded down the tube length, with its position and characteristic features being photographed by high-speed cameras. Gravitational settling and buoyancy effects were minimized because of the reduced gravity enviroment in the NASA Lewis drop towers and aircraft. Feasibility was shown as quasi-steady flame propagation which was observed for fuel-rich mixtures. Of greatest scientific interest is the finding that for near-stoichiometric mixtures, a new mode of flame propagation was observed, now called a chattering flame. These flames did not propagate steadily through the tube. Chattering modes of flame propagation are not expected to display extinction limits that are the same as those for acoustically undisturbed, uniform, quiescent clouds. A low concentration of fuel particles, uniformly distributed in a volume, may not be flammable but may be made flammable, as was observed, through induced segregation processes. A theory was developed which showed that chattering flame propagation was controlled by radiation from combustion products which heated the successive discrete laminae sufficiently to cause autoignition
A destressing "deafness" in French?
French is a language in which accent is mandatory on the last syllable of every content word. In contrast, Spanish uses accent to distinguish different lexical items (e.g., b'ebe vs beb'e). Two population of subjects were tested on the same materials to study whether such linguistic differences have an impact on the perceptual capacities of listeners. In Experiment 1, using an ABX paradigm, we find that French Subjects have a surprising deficit compared to Spanish Subjects in making accent distinctions. In Experiment 2, we find that Spanish subjects cannot ignore irrelevant differences in accent in a phoneme-based ABX task, whereas French Subjects have no difficulty at all. In Experiment 3, we replicate the basic French finding, and find that Spanish subjects benefit from redundant accent information even when phonemic information alone is sufficient to perform the task. In our final Experiment 4, we show that French subjects can hear the acoustic correlates of accent; their problem seem to arise at the level of short term memory. Implications for language-specific processing and acquisition are discussed
Recognition of Isolated Words using Zernike and MFCC features for Audio Visual Speech Recognition
Automatic Speech Recognition (ASR) by machine is an attractive research topic
in signal processing domain and has attracted many researchers to contribute in
this area. In recent year, there have been many advances in automatic speech
reading system with the inclusion of audio and visual speech features to
recognize words under noisy conditions. The objective of audio-visual speech
recognition system is to improve recognition accuracy. In this paper we
computed visual features using Zernike moments and audio feature using Mel
Frequency Cepstral Coefficients (MFCC) on vVISWa (Visual Vocabulary of
Independent Standard Words) dataset which contains collection of isolated set
of city names of 10 speakers. The visual features were normalized and dimension
of features set was reduced by Principal Component Analysis (PCA) in order to
recognize the isolated word utterance on PCA space.The performance of
recognition of isolated words based on visual only and audio only features
results in 63.88 and 100 respectively
Audio-Visual Speaker Diarization Based on Spatiotemporal Bayesian Fusion
Speaker diarization consists of assigning speech signals to people engaged in
a dialogue. An audio-visual spatiotemporal diarization model is proposed. The
model is well suited for challenging scenarios that consist of several
participants engaged in multi-party interaction while they move around and turn
their heads towards the other participants rather than facing the cameras and
the microphones. Multiple-person visual tracking is combined with multiple
speech-source localization in order to tackle the speech-to-person association
problem. The latter is solved within a novel audio-visual fusion method on the
following grounds: binaural spectral features are first extracted from a
microphone pair, then a supervised audio-visual alignment technique maps these
features onto an image, and finally a semi-supervised clustering method assigns
binaural spectral features to visible persons. The main advantage of this
method over previous work is that it processes in a principled way speech
signals uttered simultaneously by multiple persons. The diarization itself is
cast into a latent-variable temporal graphical model that infers speaker
identities and speech turns, based on the output of an audio-visual association
process, executed at each time slice, and on the dynamics of the diarization
variable itself. The proposed formulation yields an efficient exact inference
procedure. A novel dataset, that contains audio-visual training data as well as
a number of scenarios involving several participants engaged in formal and
informal dialogue, is introduced. The proposed method is thoroughly tested and
benchmarked with respect to several state-of-the art diarization algorithms.Comment: 14 pages, 6 figures, 5 table
Military applications of automatic speech recognition and future requirements
An updated summary of the state-of-the-art of automatic speech recognition and its relevance to military applications is provided. A number of potential systems for military applications are under development. These include: (1) digital narrowband communication systems; (2) automatic speech verification; (3) on-line cartographic processing unit; (4) word recognition for militarized tactical data system; and (5) voice recognition and synthesis for aircraft cockpit
Unsupervised Spoken Term Detection with Spoken Queries by Multi-level Acoustic Patterns with Varying Model Granularity
This paper presents a new approach for unsupervised Spoken Term Detection
with spoken queries using multiple sets of acoustic patterns automatically
discovered from the target corpus. The different pattern HMM
configurations(number of states per model, number of distinct models, number of
Gaussians per state)form a three-dimensional model granularity space. Different
sets of acoustic patterns automatically discovered on different points properly
distributed over this three-dimensional space are complementary to one another,
thus can jointly capture the characteristics of the spoken terms. By
representing the spoken content and spoken query as sequences of acoustic
patterns, a series of approaches for matching the pattern index sequences while
considering the signal variations are developed. In this way, not only the
on-line computation load can be reduced, but the signal distributions caused by
different speakers and acoustic conditions can be reasonably taken care of. The
results indicate that this approach significantly outperformed the unsupervised
feature-based DTW baseline by 16.16\% in mean average precision on the TIMIT
corpus.Comment: Accepted by ICASSP 201
Production and perception of speaker-specific phonetic detail at word boundaries
Experiments show that learning about familiar voices affects speech processing in many tasks. However, most studies focus on isolated phonemes or words and do not explore which phonetic properties are learned about or retained in memory. This work investigated inter-speaker phonetic variation involving word boundaries, and its perceptual consequences. A production experiment found significant variation in the extent to which speakers used a number of acoustic properties to distinguish junctural minimal pairs e.g. 'So he diced them'—'So he'd iced them'. A perception experiment then tested intelligibility in noise of the junctural minimal pairs before and after familiarisation with a particular voice. Subjects who heard the same voice during testing as during the familiarisation period showed significantly more improvement in identification of words and syllable constituents around word boundaries than those who heard different voices. These data support the view that perceptual learning about the particular pronunciations associated with individual speakers helps listeners to identify syllabic structure and the location of word boundaries
Static Visual Spatial Priors for DoA Estimation
As we interact with the world, for example when we communicate with our
colleagues in a large open space or meeting room, we continuously analyse the
surrounding environment and, in particular, localise and recognise acoustic
events. While we largely take such abilities for granted, they represent a
challenging problem for current robots or smart voice assistants as they can be
easily fooled by high degree of sound interference in acoustically complex
environments. Preventing such failures when using solely audio data is
challenging, if not impossible since the algorithms need to take into account
wider context and often understand the scene on a semantic level. In this
paper, we propose what to our knowledge is the first multi-modal direction of
arrival (DoA) of sound, which uses static visual spatial prior providing an
auxiliary information about the environment to suppress some of the false DoA
detections. We validate our approach on a newly collected real-world dataset,
and show that our approach consistently improves over classic DoA baselinesComment: 6 pages, 6 figures, 3 table
Generation of Infra sound to replicate a wind turbine
We have successfully produced infrasound, as a duplicate of that produced by
Industrial Wind Turbines. We have been able to produce this Infrasound inside a
research chamber, capable of accommodating a human test subject. It is our
vision that this project will permit others, with appropriate medical training
and ethical oversight, to research human thresholds and the effects of this
infrasound on humans. Our role has focused on producing the tools, systems, and
hardware required, to permit this research to go forward. This paper describes
the evolution of our project from the original vision, through the construction
of proof of concept prototypes, a series of improved models and their
associated accessories /operating systems, to the final test chamber as it
stands now ready to deploy. Also included are the mathematical and
computational data supporting our claim that infrasound conditions inside the
chamber can be made to duplicate those from actual Industrial wind turbines at
approved setback distances.Comment: Keywords: Infra sound, wind turbines, acoustics, sound measurement,
sound generatio
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