What will be the shape of the graph of the speed of sound in air versus pressure at a constant temperature?

$A$ sound wave of frequency $v \text{ Hz}$ initially travels a distance of $1 \text{ km}$ in air. Then, it gets reflected into a water reservoir of depth $600 \text{ m}$. The frequency of the wave at the bottom of the reservoir is $(V_{\text{air}} = 340 \text{ m/s}, V_{\text{water}} = 1484 \text{ m/s})$

What is the phase difference between the displacement wave and the pressure wave in a sound wave?

$A$ nuclear bomb exploded $200 \,km$ above the surface of the moon. The sound of the explosion on the moon

The Earth has a radius of $6400 \ km$. The inner core of $1000 \ km$ radius is solid. Outside it,there is a region from $1000 \ km$ to a radius of $3500 \ km$ which is in a molten state. Then again from $3500 \ km$ to $6400 \ km$,the Earth is solid. Only longitudinal $(P)$ waves can travel inside a liquid. Assume that the $P$ wave has a speed of $8 \ kms^{-1}$ in solid parts and of $5 \ kms^{-1}$ in liquid parts of the Earth. An earthquake occurs at some place close to the surface of the Earth. Calculate the time after which it will be recorded in a seismometer at a diametrically opposite point on the Earth if the wave travels along the diameter.

$A$ steel rod of length $100 \, cm$ is clamped at the middle. The frequency of the fundamental mode for the longitudinal vibrations of the rod is ..... $kHz$ (Speed of sound in steel $= 5 \, km \, s^{-1}$)