One tricky thing about working with time series data, like the audio data in our "um" detector (remember that?  because we barely do...), is that sometimes events look really similar but one is a little bit stretched and squeezed relative to the other.  Besides having an amazing name, the dynamic time warp is a handy algorithm for aligning two time series sequences that are close in shape, but don't quite line up out of the box.

Relevant link:
http://www.aaai.org/Papers/Workshops/1994/WS-94-03/WS94-03-031.pdf

Um Detector 2: The Dynamic Time Warp

Linear Digressions