Two loudspeakers directly face each other $30 \mathrm{m}$ apart, with the left speaker positioned at $x=0 \mathrm{m}$. The pressure of the sound wave emitted by the left speaker is described by the equation $\Delta p_{\mathrm{L}}=p_{0} \cos (1.90 x-630 t),$ while that from the right speaker is given by $\Delta p_{\mathrm{R}}=p_{0} \cos (1.90 x+630 t),$ where $x$ is measured in $\mathrm{m}$ and $t$ in $\mathrm{s}$. What is the point nearest to the left speaker at which there is a node in the sound wave?