Systems Seminar

Beat Tracking and the Search for Regularity in Complex Data

Prof. Bill Sethares
UW ECE Department

Abstract

Humans are very good at identifying complex patterns: the auditory system easily senses intricate periodicities such as the rhythms that normally occur in music and speech, the visual system readily grasps the symmetries and repetitions inherent in textures and tilings, the mind searches for simple underlying regularities to explain phenomena that appear complex and irregular. Computers are comparatively poor at locating such patterns. Beat tracking methods attempt to automatically synchronize to complex nonperiodic (yet repetitive) waveforms; to create an algorithm that can "tap its foot" in time with the music. The beat tracking problem is important as a step in understanding how people process temporal information and has direct applications in the editing of audio/video data, in synchronization of visuals with audio, in audio information retrieval and in audio segmentation.

This talk discusses a method of determining the beat from digitized audio that is based on two ideas. The first is a method of data reduction that creates a collection of ``rhythm tracks'' which represent the rhythmic structure of the piece. Each track uses a different method of (pre)processing the audio, and so provides a (somewhat) independent representation of the beat. The second idea is to model the rhythm tracks (in simplified form) as a collection of random variables with changing variances: the variance is small when "between" the beats and large when "on" the beat. Exploiting this simple stochastic model of the rhythm tracks allows the beat detection to proceed using Bayesian methods.

Audio examples are used to highlight the strengths and weaknesses of the proposed method.

Time and Place: Wed., Nov. 17, at 3:30 pm in 4610 Engr. Hall.

SYSTEMS SEMINAR WEB PAGE: http://homepages.cae.wisc.edu/~gubner/seminar/

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