Also from Catholic.com:
Full QuestionWhen is it appropriate to applaud at Mass? To do so appears to reduce the Mass to the level of entertainment, but so many people do it nowadays that I'd like to know if the Church has any teaching about it.
AnswerThere is no Church document specifying applause as an appropriate liturgical response to music, singing, homilies, or announcements of gratitude by the presider.
Although the Church does not explicitly state that applause is inappropriate at Mass, that may be because such a stricture used to be enforced by Western society. As a matter of traditional Western etiquette, it used to be severely frowned upon to applaud in church because church services are worship offered up to God and not entertainment to be critiqued by the assembly.
Now that society has generally lost the sense that applause is inappropriate in church, I suspect that the Church may soon have to speak on the matter before people take the idea to its logical conclusion and begin to boo when they are insufficiently entertained at Mass.