Vibrations

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Vibrations

The Speed of SoundSound waves pass through everything. They go through gas like the air. They gothrough liquid like the ocean. They even go through solids like the ground. The atomsvibrate along with the sound wave. The speed of sound changes when it goes throughdifferent things. Sound waves move:• slowly through gases.• more quickly through liquids.• fastest through solids.Heat also affects the speed of moving sound waves. Hot things let sound movefaster.Sound travels about 343 meters (1,125 feet) per second. That is like traveling 1,217kilometers (756 miles) per hour!Comprehension QuestionWhat is sound?Bats use sound to sensethe world around them.94#50161—Leveled Texts for Science: Physical Science© Shell Education


VibrationsPut your fingers on your throat and hum. What doyou feel? Your can feel vibrations in your throat whenyou use your voice. This is because your body makesnoise–your voice–by vibrating your voice box.Sound comes from vibrations. The atoms andmolecules that make up the air are always moving.When they move in a pattern, it creates waves. As thewaves move through matter, they cause vibrations. Thevibrations are picked up by the ear and sent as messagesto the brain. The brain turns them into the sounds wehear.Sound WavesSounds waves are compression (KOM-presh-un)waves. That means that they are made of atoms beingthe voice boxpushed, or compressed, by other atoms. Think of a bigmovie explosion. It starts small, but it pushes outward. That pushes the air around itfarther out. That air pushes more air. A sound wave is just like that. It is a vibration ofatoms pushing more atoms to vibrate the same way.Not all sound waves are alike. The differences let us hear various sounds. Scientistshave discovered that sounds and sound waves differ in the following ways:AmplitudeAmplitudeHigh Frequency Sound WaveWavelengthLow Frequency Sound WaveWavelength• Wavelength is the length from wave towave.• Amplitude is measured in the height of thesound wave. It relates to the loudness orsoftness of a sound. When a wave is high,the sound is loud. The amplitude is large.When a wave is low, the sound is soft. Theamplitude is small.• Frequency of sound relates to speed. Thenumber of vibrations per second is thefrequency. The brain turns frequency intopitch. Fast vibrations cause high pitch.Slower vibrations make lower-pitchedsounds. A tweeting bird makes a highpitchedsound. A roaring lion makes alow-pitched sound.95© Shell Education #50161—Leveled Texts for Science: Physical Science


VibrationsPut your fingers on your throat and hum. What doyou feel? Your can feel vibrations in your throat whenyou use your voice. This is because your body makesnoise–your voice–by vibrating membranes in your voicebox.Sound comes from vibrations. The atoms andmolecules that make up the air are always moving.When they move in a pattern, it creates waves. As thewaves move through matter, they cause vibrations. Thevibrations are picked up by the ear and sent as impulsesto the brain. The brain translates them as the soundswe hear.Sound WavesSounds waves are compression (KOM-presh-un)the voice boxwaves. That means that they are made of atoms beingpushed, or compressed, by other atoms. Think of a big movie explosion. It starts small,but it pushes outward. That pushes the air around it farther out. That air pushes moreair. A sound wave is just like that. It is a vibration of atoms pushing more atoms tovibrate the same way.Not all sound waves are alike. The differences let us hear various sounds. Scientistshave discovered that sounds and sound waves differ in the following ways:AmplitudeAmplitudeHigh Frequency Sound WaveWavelengthLow Frequency Sound WaveWavelength• Wavelength is the distance between thetroughs on either side of a single wave.• Amplitude is measured in the height ofthe sound wave. It relates to loudness orsoftness of a sound. When a wave is high,the sound is loud and the amplitude islarge. When a wave is low, the amplitude issmall and the sound is soft.• Frequency of sound relates to speed.The number of vibrations per second isthe frequency. The brain understandsfrequency as pitch. Fast vibrations causehigh pitch. Slower vibrations make lowerpitchedsounds. A tweeting bird makes ahigh-pitched sound. A roaring lion makesa low-pitched sound.97© Shell Education #50161—Leveled Texts for Science: Physical Science


The Speed of SoundThe vibrations of sound waves penetrate all states of matter, including gas,liquid, and solid. No matter what state they are in, the atoms still vibrate becauseof the sound wave’s vibrations. However, the speed of sound changes as itpenetrates different states of matter. Sound waves move:• slowly through gases.• more quickly through liquids.• fastest through solids.Temperature also affects the speed of moving sound waves. Higher temperaturescause sound to move faster. At normal room temperatures, sound travels about 343meters (1,125 feet) per second. That is like traveling 1,217 kilometers (756 miles)per hour!Bats use sound to sensethe world around them.Comprehension QuestionDescribe how sound waves are related tovibrations.100#50161—Leveled Texts for Science: Physical Science© Shell Education

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