Sound waves travel fast you know that because you hear music while its begin played. it travels to your ears through a gas-the air . Sound waves can also travel through solids and liquids . if someone knocks on a door . the sound goes through a solid . some sea animals communicate underwater using sound sound can move even more quickly through solids and liquids than it does through gases . How loud a sound is can also depend on the material it passer through . try this fill a plastic bag with cotton and fill the bug with air listen to the clock again through the bag was the ticking louder through cotton or air? why? how loud do you think the ticking would be if you put a wooden block between your ear and the clock? try it
Remember that sound waves spread outward until they hit a hard flat surface they bounce back . sometimes they bounce off in exactly the same pattern in which they hit then you hear an echo empty rooms and mountain caves often produce echoes