The Nature of Sound

The Nature of Sound

Physical SciencePhysical Science

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What is Sound?What is Sound?

• Sound comes from vibrations that move in a series of compressions and rarefactions (longitudinal waves).

• A tree falls in the woods when no one is around. Did it make a sound?

• There is a difference between creating a sound and detecting a sound.

• Sound comes from vibrations that move in a series of compressions and rarefactions (longitudinal waves).

• A tree falls in the woods when no one is around. Did it make a sound?

• There is a difference between creating a sound and detecting a sound.

The Human EarThe Human Ear

Outer ear: Funnel for sound waves – directs vibrations to ear canal.

• Middle ear: 3 bones act as levers to increase (amplify) the vibrations (Where eardrum is located).

• Inner ear: Vibrations turn into electrical signals for the brain to interpret. Vibrations cause waves in liquid inside the cochlea, which sends the electric signals to the brain.

Outer ear: Funnel for sound waves – directs vibrations to ear canal.

• Middle ear: 3 bones act as levers to increase (amplify) the vibrations (Where eardrum is located).

• Inner ear: Vibrations turn into electrical signals for the brain to interpret. Vibrations cause waves in liquid inside the cochlea, which sends the electric signals to the brain.

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How the Ear WorksHow the Ear Works

• http://www.youtube.com/watch?v=0ivY7CoACXU&feature=related&safety_mode=true&persist_safety_mode=1

• http://www.youtube.com/watch?v=0ivY7CoACXU&feature=related&safety_mode=true&persist_safety_mode=1

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Causes of Hearing Loss/Deafness

Causes of Hearing Loss/Deafness

• Tinnitus – hearing loss due to long-term exposure to loud sounds (“ringing” in ears).

• Deafness can occur from serious tinnitus or any damage to any of the parts of the ear. (How safe are Q-tips?)

• Ear protection is important when exposed to unusually loud noises.

• Tinnitus – hearing loss due to long-term exposure to loud sounds (“ringing” in ears).

• Deafness can occur from serious tinnitus or any damage to any of the parts of the ear. (How safe are Q-tips?)

• Ear protection is important when exposed to unusually loud noises.

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Sound Speed and Temperature

Sound Speed and Temperature

• Cooler temperatures slow down the speed of sound (air particles move slower).

• Since cooler temperatures lower the speed of sound, why is it easier for pilots to break the sound barrier while flying?

• Cooler temperatures slow down the speed of sound (air particles move slower).

• Since cooler temperatures lower the speed of sound, why is it easier for pilots to break the sound barrier while flying?

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Changing the Speed: How the Hindenburg disaster really sounded

Changing the Speed: How the Hindenburg disaster really sounded

• http://www.youtube.com/watch?v=pUVDmXvXcbk&safety_mode=true&persist_safety_mode=1&safe=active

• http://www.youtube.com/watch?v=pUVDmXvXcbk&safety_mode=true&persist_safety_mode=1&safe=active

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Properties of SoundProperties of Sound

• Speed – Since sound requires a medium, then speed can increase/decrease, depending on resistance of the medium.

• Sound can speed up or slow down (travels 3 times faster in helium)

• Sound waves travel faster through many solid objects (i.e., wood, glass, steel, etc.)

• Speed – Since sound requires a medium, then speed can increase/decrease, depending on resistance of the medium.

• Sound can speed up or slow down (travels 3 times faster in helium)

• Sound waves travel faster through many solid objects (i.e., wood, glass, steel, etc.)

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Pitch and Frequency of Sound

Pitch and Frequency of Sound

• The “highness” or “lowness” of sound is the pitch.

• Pitch depends on the frequency of the sound waves (1 Hz = 1 wave per sec.)

• Humans can hear frequencies between 20 Hz and 20,000 Hz (depends on age).

• The “highness” or “lowness” of sound is the pitch.

• Pitch depends on the frequency of the sound waves (1 Hz = 1 wave per sec.)

• Humans can hear frequencies between 20 Hz and 20,000 Hz (depends on age).

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Pitch and Frequency of Sound

Pitch and Frequency of Sound

• Infrasonic – Sounds with frequencies lower than 20 Hz (outside of range of human hearing)

• Ultrasonic – Sounds with frequencies greater than 20,000 Hz (Too high for hearing, can be used for cleaning jewelry.)

• Infrasonic – Sounds with frequencies lower than 20 Hz (outside of range of human hearing)

• Ultrasonic – Sounds with frequencies greater than 20,000 Hz (Too high for hearing, can be used for cleaning jewelry.)

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UltrasoundUltrasound

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Hear the reaction of a couple who find out they are having twins!

http://www.youtube.com/watch?v=1EStMIHpFow&safety_mode=true&persist_safety_mode=1

The Doppler EffectThe Doppler Effect

• The Doppler Effect is a change in sound cased by either the motion of the listener or the source of the sound.

• Imagine a car, honking its horn, as it comes towards you, getting louder and louder. What does it sound like after it passes you?

• The Doppler Effect is a change in sound cased by either the motion of the listener or the source of the sound.

• Imagine a car, honking its horn, as it comes towards you, getting louder and louder. What does it sound like after it passes you?

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Amplitude in Sound = Loudness

Amplitude in Sound = Loudness

• In sound, when you increase the amplitude of a wave, you increase the loudness of that wave.

• Loudness is measured in decibels. Human ears hear at an average of 0 db-70 db. 120 db is called the “pain threshold”. Continued exposure to sounds above 85 db can cause gradual but permanent hearing loss.

• In sound, when you increase the amplitude of a wave, you increase the loudness of that wave.

• Loudness is measured in decibels. Human ears hear at an average of 0 db-70 db. 120 db is called the “pain threshold”. Continued exposure to sounds above 85 db can cause gradual but permanent hearing loss.

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Common Noises and Their Decibel Levels

Common Noises and Their Decibel Levels

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Aircraft at take-off (180) Fireworks (140) Snowmobile (120) Chain saw (110) Amplified music (110) Lawn mower (90) Noisy office (90) Vacuum cleaner (80) City traffic (80) Normal conversation (60) Refrigerator humming (40) Whisper (20) Noise levels of 130 decibels or over will be painful and is very likely to cause immediate hearing damage.

Transferring Sound to PaperTransferring Sound to Paper

• Sound waves can be received and then graphed on paper. The instrument that can do this is called an oscilloscope.

• Sound waves can be received and then graphed on paper. The instrument that can do this is called an oscilloscope.

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Interactions of Sound WavesInteractions of Sound Waves

• Echolocation – When sound is sent out and reflects back to find an object or location.

- Sonar – Type of electronic echolocation

Uses short ultrasonic wavelengths

(often used on ships)

- Ultrasongraphy – Ultrasound uses sound waves (not xrays) to bounce off organs and create a “picture” of them.

• Echolocation – When sound is sent out and reflects back to find an object or location.

- Sonar – Type of electronic echolocation

Uses short ultrasonic wavelengths

(often used on ships)

- Ultrasongraphy – Ultrasound uses sound waves (not xrays) to bounce off organs and create a “picture” of them.

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Dolphin Using EcholocationDolphin Using Echolocation

• http://www.youtube.com/watch?v=51G83jaeNC4&safety_mode=true&persist_safety_mode=1

• http://www.youtube.com/watch?v=51G83jaeNC4&safety_mode=true&persist_safety_mode=1

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The Sound BarrierThe Sound Barrier

• Since the source of sound, like a jet plane, accelerates to the speed of sound, the sound waves in front compress together. If the jet accelerates pass the speed of sound, a tremendous shock wave results.

• Since the source of sound, like a jet plane, accelerates to the speed of sound, the sound waves in front compress together. If the jet accelerates pass the speed of sound, a tremendous shock wave results.

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Sonic Boom!Sonic Boom!

• When the shock waves reach your ears, you hear a large explosive sound. Sonic booms are large enough to cause ear damage and some minor damage.

• http://www.youtube.com/watch?v=XZMK7pCtVNk&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

• http://www.youtube.com/watch?v=6o0zmafxTmE&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

• When the shock waves reach your ears, you hear a large explosive sound. Sonic booms are large enough to cause ear damage and some minor damage.

• http://www.youtube.com/watch?v=XZMK7pCtVNk&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

• http://www.youtube.com/watch?v=6o0zmafxTmE&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

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