This is small project I whipped together by pulling information off Twitter's API during the 2011 State of the Union Address, and then running the data through a senitment analysis to gauge audience reaction throughout the speech. The result:

This graph represents the ratio of positive words to negative words over time during the SOTU.

For reference, Pres. Obama's speech began and ended at approximately 9:11PM and 10:13PM. To compare, here's a timeline of selected quotes and topics discussed during the speech:

If you're interested in further comparing the data to the speech, I recommend the White House video of the SOTU on Youtube, which has a full transciption timeline. Simply add 9 hours and 11 minutes to the video time to estimate the time in EST.

The data includes 240,000 tweets which use the term "sotu", "#sotu", "stateoftheunion" or "state of the union", sent between 9:00PM and 10:30PM EST on 1/25/2011.

Every tweet was compared to a list of words with predetermined sentiment scores (from the University of Pittsburgh's OpinionFinder subjectivity lexicon). Each tweet was given two scores, one for the number of matched positive words and another for number of matched negative words. The scores were then summed up by 10 second time intervals, and a sentiment ratio (total positive words / total negative words) was generated for each 10s interval. The ratio is represented on the above graph as the gray line. The magenta line is a 60 second moving average, and the navy line is a 5 minute moving average.

This methodology is nearly identical to that of a study by Carnegie Mellon (O’Connor et al. 2010), which was featured on Mashable and other blogs. As noted in that study, there are lexicons that may work much better with Twitter, as this one was developed for proper English, which is something of a rarity on Twitter. ("#zomg4reels.")