In this demonstration, students use their bodies to model vibrations that lead to sound waves. Show
Three things vibrate when sound is created:
When a sound is produced, it causes the air molecules to bump into their neighbouring molecules, who then bump into their neighbours, and so on. There is a progression of collisions that pass through the air as a sound wave. Air itself does not travel with the wave (there is no gush or puff of air that accompanies each sound); each air molecule moves away from a rest point and then, eventually, returns to it. When we hear something, we are sensing the vibrations in the air. The number of vibrations per second is known as the frequency, measured in Hertz (1 Hz = 1 vibration per second). These vibrations enter the outer ear and cause the eardrum to vibrate too. We cannot hear the vibrations that are made by waving our hands in the air because they are too slow. The slowest vibration our human ears can hear is 20 times a second. That would be a very low sound. The fastest vibration we can hear is 20,000 times per second, which would be a very high sound. Animals can hear different frequencies from humans. Cats can hear even higher frequencies than dogs, and porpoises can hear the fastest vibrations of all (up to 150,000 times per second).
It takes 3 different vibrations to hear a sound, since sound is made when things vibrate (or wiggle) :
When sound waves move through the air, each air molecule vibrates back and forth, hitting the air molecule next to it, which then also vibrates back and forth. The individual air molecules do not "travel" with the wave. They just vibrate back and forth. When the vibrations are fast (high frequency), you hear a high note. When vibrations are slower, you hear a lower note. Sound is all about vibrations. The source of a sound vibrates, bumping into nearby air molecules which in turn bump into their neighbours, and so forth. This results in a wave of vibrations travelling through the air to the eardrum, which in turn also vibrates. What the sound wave will sound like when it reaches the ear depends on a number of things such as the medium it travels through and the strength of the initial vibration.
In the following activities, students will use simple materials to create, visualize and feel sound waves, investigate vibration and its role in producing sound, and make their own percussion instruments. List of Activities:Sound = Vibration, Vibration, Vibration
Objectives
Materials
BackgroundSound is a type of energy made by vibrations. When an object vibrates, it causes movement in surrounding air molecules. These molecules bump into the molecules close to them, causing them to vibrate as well. This makes them bump into more nearby air molecules. This “chain reaction” movement, called sound waves, keeps going until the molecules run out of energy. As a result, there is a series of molecular collisions as the sound wave passes through the air, but the air molecules themselves don’t travel with the wave. As it is disturbed, each molecule just moves away from a resting point but then eventually returns to it. Pitch and Frequency Pitch is related to frequency, but they are not exactly the same. Frequency is the scientific measure of pitch. That is, while frequency is objective, pitch is completely subjective. Sound waves themselves do not have pitch; their vibrations can be measured to obtain a frequency, but it takes a human brain to map them to that internal quality of pitch. The pitch of a sound is largely determined by the mass (weight) of the vibrating object. Generally, the greater the mass, the more slowly it vibrates and the lower the pitch. However, the pitch can be altered by changing the tension or rigidity of the object. For example, a heavy E string on an instrument can be made to sound higher than a thin E string by tightening the tuning pegs, so that there is more tension on the string. Nearly all objects, when hit, struck, plucked, strummed or somehow disturbed, will vibrate. When these objects vibrate, they tend to vibrate at a particular frequency or set of frequencies. This is known as the natural frequency of the object. For example, if you ‘ping’ a glass with your finger, the glass will produce a sound at a pitch that is its natural frequency. It will make this same sound every time. This sound can be changed, however, by altering the vibrating mass of the glass. For example, adding water causes the glass to get heavier (increase in mass) and thus harder to move, so it tends to vibrate more slowly and at a lower pitch. What
is Sound? The properties of a sound wave change when it travels through different media: gas (e.g. air), liquid (e.g. water) or solid (e.g. bone). When a wave passes through a denser medium, it goes faster than it does through a less-dense medium. This means that sound travels faster through water than through air, and faster through bone than through water. When molecules in a medium vibrate, they can move back and forth or up and down. Sound energy causes the molecules to move back and forth in the same direction that the sound is travelling. This is known as a longitudinal wave. (Transverse waves occur when the molecules vibrate up and down, perpendicular to the direction that the wave travels). Speaking (as well as hearing) involves vibrations. To speak, we move air past our vocal cords, which makes them vibrate. We change the sounds we make by stretching those vocal cords. When the vocal cords are stretched we make high sounds and when they are loose we make lower sounds. This is known as the pitch of the sound. The sounds we hear every day are actually collections of simpler sounds. A musical sound is called a tone. If we strike a tuning fork, it gives off a pure tone, which is the sound of a single frequency. But if we were to sing or play a note on a trumpet or violin, the result is a combination of one main frequency with other tones. This gives each musical instrument its characteristic sound. Fun Facts!
Vocabularyamplification: The process of increasing or making stronger. Other ResourcesScience World | YouTube | Sound Science World | YouTube| The Sound Show Canada Science and Technology Museum |Strin-o-lin Online Tuning Forks Artists Helping Children: Arts & Crafts | Musical Instrument Crafts for Kids Science Kids at Home | What is Sound? To purchase Boomwhackers: What are the movement of air molecules brought about by a source of vibration?When an object vibrates, it causes movement in surrounding air molecules. These molecules bump into the molecules close to them, causing them to vibrate as well. This makes them bump into more nearby air molecules. This “chain reaction” movement, called sound waves, keeps going until the molecules run out of energy.
What is it called when physical stimuli produce errors in perception?Sensory-perceptual alteration can be defined as when there is a change in the pattern of sensory stimuli followed by an abnormal response to such stimuli. Such perceptions could be increased, decreased, or distorted with the patient's hearing, vision, touch sensation, smell, or kinesthetic responses to stimuli.
Which of the following are bones that are contained in the middle ear which both transmit vibrations and increase their strength?The Middle Ear
The vibrations from the eardrum set the ossicles into motion. The ossicles are actually tiny bones — the smallest in the human body. The three bones are named after their shapes: the malleus (hammer), incus (anvil) and stapes (stirrup). The ossicles further amplify the sound.
What does absolute threshold mean in psychology?The "absolute threshold of sensation" refers to the minimum intensity of a stimulus that a person can detect half the time. This threshold is not fixed, but varies from person to person and can be influenced by psychological factors, such as expectations, motivation, and alertness.
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