Manipulate[Plot[Sinc[ω t - (Subscript[ω, 0])] + Sinc[ω t+(Subscript[ω, 0])], {t, -r, r}, PlotRange->{-0.3,1.2}],{{r, 30},5,40}, {{(Subscript[ω, 0]), 28}, 1, 50}, {{ω, 2}, 1, 10}] (* /. {(Subscript[ω, 0]) -> 28, ω -> 2} *)