Would sound travel faster in a thick piece of metal (high density) or a large hollow piece of metal (low density)?

See the explanation below

Explanation:

The speed of sound waves can be calculated using the following equation:

Let's do the exercise of comparing two materials one denser than the other, as is steel and aluminum

ro_steel = 7500 [kg/m^3]

ro_aluminum = 2700 [kg/m^3]

E_steel = 200 [GPa]

E_aluminum = 70 [GPa]

Now replacing the values in the equation for each material.

And for the aluminum

In this way we can see that sound propagates faster in denser materials.

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.