Answer:
Particles of matter are packed more tightly in the ground than in the air.
Step-by-step explanation:
As we know that velocity of sound in a given medium is given by formula

here we know that
E = elasticity of the medium
= density of the medium
now we know that if we increase the density of medium then particles of matter are packed more which will decrease the speed of wave.
while is particles are tightly packed then it will increase the elasticity of the medium
So here if all particles are tightly bounded with each other then sound waves will move faster through the medium