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We know sound travels faster through solids than through air.

Now consider this: Perhaps two people A & B are standing in two adjacent rooms both of which are closed from all sides. Let distance between A & B be d units. Now, B shouts and A hears the shout with a particular volume.

Next the rooms are removed and again B shouts , while the distance between A & B remains d units. This time A hears the shout at a much louder volume than in the previous case.

But how is this possible? Doesn't sound travel more efficiently through solids ? That means in the 1st case, the sound should have traveled through the walls of the room faster and reached A from B with a much larger volume than in the 2nd case, as, in the 2nd case, the sound travels through air which means it should have traveled slower.

But that does not happen. How?

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The volume doesn't determine the speed of sound. The volume is lower because some sound waves get absorbed and reflected back when they hit the wall which makes the amplitude smaller and therefore the volume is lower.

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  • $\begingroup$ What happens if instead there was no wall, but both of them are submerged in water (higher density $\implies$ higher speed of sound) and instead of shouting they used some different mechanism of producing sound. Since in this case there is no reflection, would there be a difference in volume (sound intensity) ? I know this is not OP's question but I think it might help clarify what's happening. $\endgroup$ – Stratiev Jun 25 '20 at 9:21
  • $\begingroup$ @Stratiev According to me , u cant hear voices at all if u r submerged underwater. $\endgroup$ – Bhavay Jun 25 '20 at 9:44
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    $\begingroup$ You can't discern voices underwater, but that doesn't mean you can't hear any sound whatsoever, which is why I included my clarification about using "some different mechanism of producing sound". $\endgroup$ – Stratiev Jun 25 '20 at 10:23
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Like Ken mention in their answer, the speed of sound does NOT determine the amplitude of the sound. This means that you can't really rely on one to make any conclusions about the other (at least not in a direct way).

Additionally (like Ken also mentioned), in the first case (room boundaries present) the volume will be lower in the position of B because some of the energy (the amount depends on many factors such as the material(s) and composition of the boundaries, the frequency of sound, the way the boundaries are connected - flanking transmission - and some more) is reflected back into the room where A is positioned and some is dissipated as heat inside the material of the walls.

Reflection takes place due to the impedance mismatch of the media (air and wall material) and dissipation, mostly due to internal loses at the media (most of the loss mechanisms are a bit complex to discuss here).

Now, Stratiev gave a nice hint on clarifying a bit the given answers by providing an indirect question on the connection between the medium in which sound travels (this also determines the speed of sound) and the volume.

Assuming homogeneous media (this may not be a valid assumption for water when the travelling distance is quite long and under certain conditions), the speed of sound is constant as well as the loss mechanisms. Again, what determines the volume difference at the position of B in the two cases (assuming the same radiated power with the same directivity of course) are the loses exhibited in each medium. Thus, once more, the speed of sound is not directly related to the volume at the position of B for a homogeneous medium and for constant environmental conditions.

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