Put it at the start of the scene, right after the empty chair is shown, then follow it with a sudden suspense sting while everyone waits for a reply, and finish with Nelson's teasing laugh once the missing friend finally shows up.
關於此聲音
It is a short Tamil voice line, just under three seconds long, in which a speaker asks 'dei, engada irukinga' – hey, where are you? – with a teasing, impatient edge. It feels funny and lightly scolding, like a friend chasing a reply that never came, rather than genuinely angry. The line comes from everyday Tamil slang used between friends.