6,186 research outputs found
The Reliability Function of Lossy Source-Channel Coding of Variable-Length Codes with Feedback
We consider transmission of discrete memoryless sources (DMSes) across
discrete memoryless channels (DMCs) using variable-length lossy source-channel
codes with feedback. The reliability function (optimum error exponent) is shown
to be equal to where is the rate-distortion
function of the source, is the maximum relative entropy between output
distributions of the DMC, and is the Shannon capacity of the channel. We
show that, in this setting and in this asymptotic regime, separate
source-channel coding is, in fact, optimal.Comment: Accepted to IEEE Transactions on Information Theory in Apr. 201
Detection of nonverbal vocalizations using Gaussian Mixture Models: looking for fillers and laughter in conversational speech
In this paper, we analyze acoustic profiles of fillers (i.e. filled pauses, FPs) and laughter with the aim to automatically localize these nonverbal vocalizations in a stream of audio. Among other features, we use voice quality features to capture the distinctive production modes of laughter and spectral similarity measures to capture the stability of the oral tract that is characteristic for FPs. Classification experiments with Gaussian Mixture Models and various sets of features are performed. We find that Mel-Frequency Cepstrum Coefficients are performing relatively well in comparison to other features for both FPs and laughter. In order to address the large variation in the frame-wise decision scores (e.g., log-likelihood ratios) observed in sequences of frames we apply a median filter to these scores, which yields large performance improvements. Our analyses and results are presented within the framework of this year’s Interspeech Computational Paralinguistics sub-Challenge on Social Signals
Power Dependent Lineshape Corrections for Quantitative Spectroscopy
The Voigt profile - a convolution of a Gaussian and a Lorentzian - accurately
describes the absorption lines of atomic and molecular gases at low probe
powers. Fitting such to experimental spectra yields both the Lorentzian natural
linewidth and the Gaussian Doppler broadening. However, as the probe power
increases saturation effects introduce spurious power dependence into the
fitted Doppler width. Using a simple atomic model, we calculate power-dependent
corrections to the Voigt profile, which are parametrized by the Gaussian
Doppler width, the Lorentzian natural linewidth, and the optical depth. We show
numerically and experimentally that including the correction term substantially
reduces the spurious power dependence in the fitted Gaussian width.Comment: 4 pages, 3 figure
Direct observation of dynamic surface acoustic wave controlled carrier injection into single quantum posts using phase-resolved optical spectroscopy
A versatile stroboscopic technique based on active phase-locking of a surface
acoustic wave to picosecond laser pulses is used to monitor dynamic
acoustoelectric effects. Time-integrated multi-channel detection is applied to
probe the modulation of the emission of a quantum well for different
frequencies of the surface acoustic wave. For quantum posts we resolve
dynamically controlled generation of neutral and charged excitons and
preferential injection of holes into localized states within the nanostructure.Comment: 10 pages, 4 figure
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