"Yeah" - Normal state, no extra waves to conflict with
"Yeah yeah" - Interferes with itself becoming dismissive without contextual dampening
"Yeah yeah yeah" - Now resonates with itself creating excited harmonics without appropriate dampening
"Yeah yeah yeah yeah" - Once again causes interference and can spike into different harmonics depending on what vague context it bounces off of to the reader
"Yeah yeah yeah yeah yeah" - Resonates very strongly and tends to be heard in the voice of Dexter Holland