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Sound and Music · entry 52 of 52
Sound shadows appear behind large obstacles where direct waves cannot easily reach.
The longer version
Barriers such as walls, hills and buildings block the direct path, and a listener just behind one receives far less energy. High rates behave almost like rays and are blocked sharply, while low rates have wavelengths comparable to the obstacle and bend around it. Diffraction at the top edge still leaks some energy downward into the quiet zone.
That is the reason distant traffic is heard as a low rumble with the hiss stripped away. Purpose-built barriers along roads exploit the effect, and their benefit depends on size relative to wavelength, which is why a low fence helps far less than a tall one.
Where this entry sits
Sound and Music gathers facts about how vibrations move through air and water, how ears turn them into meaning, and how instruments and notation shape what listeners hear. Expect echoes, pitch, volume, acoustics, and the odd silence in between. The full list sits on the Sound and Music page, where every entry is listed in order.
More From Sound and Music
Eight more entriesSound travels through air as a series of compressions and rarefactions moving outward.
Read 2Sound cannot travel through a vacuum because there is no material to carry vibrations.
Read 3Sound moves faster through water than through air, and faster still through solid steel.
Read 4Thunder arrives after lightning because light travels far faster than sound through air.
Read 5An echo is simply a sound wave bouncing off a hard surface and returning to the listener.
Read 6A room with soft furnishings produces fewer echoes than an empty room with bare walls.
Read 7The human ear collects sound with a funnel of cartilage and skin called the pinna.
Read 8Tiny hair cells inside the cochlea convert vibrations into electrical signals the brain can read.
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