The person applauding alone makes appreciation visible before it becomes socially easy.

Approval in a group is mostly waiting for permission. Everyone in the room may have liked what they heard, but nobody wants to be wrong about how the room feels, so the response stalls. Whoever claps first absorbs the risk of being alone, and after two seconds the risk stops existing for everybody else. What looks like a spontaneous wave began with one person willing to be conspicuous.

Be that person more often than feels natural. Say the good thing out loud before you have checked whether others agree, because the cost to you is a moment of exposure and the benefit to someone else can be the whole evening.