Soon after I started studying applause in political speeches, it emerged that there is a ‘normal’ burst of applause that lasts for about eight (plus or minus one) seconds (see Our Masters' Voices, 1984).
Less than this and it sounds half-hearted; more than this and it sounds more enthusiastic than usual – with the result that the media are more likely to select lines that get longer bursts for headlines in newspapers or sound bites on news programmes.
Nor is this norm only to be found in political speeches, but is also to be heard in award ceremonies, at conferences when speakers are introduced or when the identity of guests on television talk shows is revealed.
A few years ago, I went to a concert by Donovan, a pop star contemporary of the Beatles. In the first half, all his performances of familiar hits from the 1960s attracted 15-20 seconds of applause (i.e. considerably more than usual), whereas none of the applause for his numbers from his latest album in the second half fell outside the standard 7-9 second range – polite enough, but nowhere near as enthusiastic as the responses to songs that the audience had known for years.
If you want to check out what the difference sounds like for yourself, compare the following two clips from President Obama's introduction to his nominee for the vacancy on the Supreme Court. In the first one, Judge Sotomayor gets a 'standard' eight-second burst of applause after saying that she loves her family; in the second one, the applause for the President's introduction to her goes on for five times longer than that.
As such, it suggests that the audience was very well pleased with the announcement. But to find out it was a more enthusiastic response than usual, we’d have to compare it with some clips of presidents introducing previous nominations for the post of Supreme Court judge.