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Senior Project – Electrical Engineering - 2010 Xkl: A Tool for Speech Analysis Eric Truslow Advisor – Prof. Hanson Xkl Abstract Xkl is a speech analysis program that requires additional Speech production is modeled as a slowly varying linear system functionality to continue being used. This project addresses consisting of a source and filter (vocal tract). Examining the this issue by adding an annotation system, and a pitch frequency composition of a speech signal over time is one way contour display. Annotation allows researchers to describe to help characterize it. Xkl displays this information using portions of speech signals. The pitch contour shows the customizable spectrogram, DFT and smooth spectrum displays. change in periodicity of a speech signal over time. Users The spectrogram displays the DFT computed in small time steps will be able to use Xkl to examine speech in ways that over the entire signal. The darkest regions have the strongest were previously impossible in Xkl. intensities and represent the filter’s resonant frequencies. Method Through a survey of the past and present users of Xkl, enhancements to the program were prioritized as follows: 1. An improved labeling system. 2. Pitch contour display. 3. Compatibility with multiple operating systems and Spectrogram in Xkl support for more audio file formats. Final Design Labeling How a human body generates a particular sound is not always immediately recognizable from a speech signal. Annotating the signal gives researchers a way to describe aspects of a signal for future reference. This is done using labels which may specify a point or interval of time. Labels are logically and visually separated into groups and may be saved in TextGrid format, which is understood by another speech analysis program Praat. Labels in Xkl Pitch Contour The pitch contour is used to characterize periodic excitations of the vocal tract, which occur when the vocal folds are vibrating. The frequency at which they vibrate is of interest because of the lexical, prosodic, and other information it carries in language. At right is a spectrogram from the program Praat with the pitch contour superimposed on it. There are many different methods to compute the pitch period, but Praat’s was selected because it is freely available Pitch contour sample and is well tested. Future Work Portability and Compatibility • Finalize labeling and pitch contour interfaces. Xkl now loads WAVE audio files and was modified to run on • Deploy to users for further feedback. OS X. Sound is played using PortAudio a cross-platform • Continue making additions to labeling system and pitch audio library. contour display. • Fix bugs and behavior as reported by users.