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The Nature of Sound. SOUND WAVES. Sound waves carry energy through a medium as a LONGITUDINAL WAVE. The ENERGY disturbs the medium by causing the particles next to each other to COMPRESS. Sound travels through solids, liquids, and gases. MAKING WAVES.
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SOUND WAVES • Sound waves carry energy through a medium as a LONGITUDINAL WAVE. • The ENERGY disturbs the medium by causing the particles next to each other to COMPRESS. • Sound travels through solids, liquids, and gases.
MAKING WAVES • All objects can be made to vibrate, by plucking, striking or blowing across. • They will vibrate at their NATURAL or FUNDAMENTAL FREQUENCY. This FREQUENCY is determined by the SIZE, SHAPE, DENSITY & MATTER the object is made of. STOMP!
SOUND WAVES INTERACT WITH MATTER • Sound waves may reflect when they hit a surface. • Sound waves can DIFFRACT through an opening, or bend around a corner.
Perception of Sound • LOUDNESS – Depends on HOW MUCH ENERGY is put behind it (amplitude). • We measure LOUDNESS in DECIBELS (dB) MORE AMPLITUDE = MORE DECIBELS = INTENSITY!
PITCH • Describes of how HIGH or LOW the sound seems. • Pitch is caused by the number of VIBRATIONS or the FREQUENCY of the sound wave.
FREQUENCY = # of waves A LOT OF VIBRATIONS = HIGH FREQUENCY = HIGH PITCH SLOW OR FEWER VIBRATIONS = LOWER FREQUENCY = LOW PITCH GLASSES
SIZE AFFECTS FREQUENCY! The SMALLER an object, the MORE the WAVE REFLECTS inside it, so… The GREATER the # of Vibrations! _________ Frequency = _______ Pitch The BIGGER an object, the SLOWER the VIBRATIONS, The LOWER the # of VIBRATIONS. _________ Frequency = _______ Pitch
HUMANS have a limited RANGE of PERCEPTION of SOUND WAVES Infrasound Ultrasound • Sound waves above the normal human range of hearing. • Sound waves below the normal human range of hearing. MOSQUITO RINGTONE HEARING TEST
Speed of Sound • Depends on the density and temperature of the medium the wave travels through. LOWER TEMP OR GREATER DENSITY = FASTEST SPEED (SOLID) HIGHER TEMP OR LOWER DENSITY = SLOWER SPEED (GAS) HANGER DEMO ANIMATION
Density • How much matter, or mass, there is in a given amount of space, or volume. Sound travels fastest in denser mediums.
Temperature • Sound travels more slowly at higher temperatures than at lower temperatures.
The Doppler Effect • The change in frequency of a sound wave caused by movement of the sound source or the observer.
What do you notice about the waves? • Wavelength? • Frequency? • What would • cause the • amplitude to • change?
What happens to the waves in front of him? • Wavelength? • Frequency? • How would this • change what • we hear? • Behind him?
Shock Waves • Form when sound waves overlap and break through the wave barrier, releasing a huge amount of energy (sonic boom!) VIDEO
THE SOUND SONG When someone’s making a sound. Well, the atoms start moving around. They vibrate into your ear. Movin your eardrum, and makin you hear. CHORUS: (I think it’s time we…) Stop, listen to that sound. Resonating through us all around! Compressions happening here Longi-tud-inal waves will appear Rar-e-factions appear over there Through solids, and liquids. Even through air!
The eardrum vibrates and repeats Hammer and anvil will pound out the beats The cochlea moves fluid around The cilia will wave – and the brain makes a sound! CHORUS: (I think it’s time we…) Stop, listen to that sound. Resonating through us all around! Be careful of the decibels you hear More than 100 might be damaging your ear The loudness can cause them to ring You’ll get tinnitus, or have trouble. Can’t hear anything!
POP GOES tHE WEASEL G CC DD EGEC G CC D F E C G CC DD EGEC A D F E C
TWINKLE TWINKLE LITTLE STAR CC GG AA G FF EE DD C GG FF EE D GG FF EE D CC GG AA G FF EE DD C
Warm-up • Why is the speed of sound faster in colder temperatures?