You smack your hands together to create noise. This noise is meant to show respect for the performer. Next time you are at a large performance and the audience claps, look around at the people and notice how funny it is. They're like monkeys smacking their asses together. Pretty funny stuff.
You'd expect that in our day and age we would have some technology that replaces clapping. Maybe a button on your seat that, when pressed, creates soothing sounds via an intercom.
Post your solutions.