Two coherent sound sources $\mathrm{A}$ and $\mathrm{B}$ produce a sound of wavelength $\mathrm{\lambda }$. If at $t=0$ a detector starts moving with constant velocity $v_0$ from point $\mathrm{O}$ along y-direction, then the minimum time,  after which it detects the sound of maximum intensity, is $\left(D >>\mathrm{\lambda }\right)$