When we change feeble sound to loud sound we increase its

The given graph shows the displacement versus time relation for a disturbance travelling with velocity of $1500 {\mathrm{ms}}^{-1}$. Calculate the wavelength of the disturbance.

Which of the above two graphs $\left(a\right)$ and $\left(b\right)$ (Fig.) representing the human voice is likely to be the male voice? Give reason for your answer.