# Why does sound travel better through solids but it is dampened when it finds a wall?

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I have been taught that a solid state medium helps the vibrations of the particles traverse better through it than in a gas state medium, so why a sound wave travels through air but it stops when it finds a solid object like a wall?

In: Physics

Because most of the sound bounces off said wall instead of traveling through it. A little will make it through the wall, which is the reason the volume decreases

Transmitting many wave-type signals, sound, radio waves etc, get disrupted when they meet parts of their route that have different resistances (impedance). At a point of change, part of the signal is reflected and part transmitted, depending on the relative impedance either side. The best transmission happens when there is no impedance change.

So once a sound wave is inside the solid, it transmits well as the impedance stays constant. A sound wave in air comes up against a change in impedance when it hits a solid wall. Only a small proportion proceeds forward into the solid, the larger part is reflected.

For this reason, the best sound absorbing material is a sandwich of alternating layers of stiff, dense material separated by air gaps or something like foam, so as the sound wave progresses, it comes upon multiple mismatches of impedance in its path.

Sound travels very easily through solid material because vibrations transfer directly. Most walls have spaces which will disperse sound waves, kind of like how light refracts through the other side of a crystal prism. Also more similarly, how seismic waves refract through earth’s layers.