The Nature of Sound Physical Science

9/7/20152 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 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. 9/7/20153

How the Ear Works Q5Wr_Ihttp:// Q5Wr_I Q5Wr_Ihttp:// Q5Wr_I 9/7/20154

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. 9/7/20155

How Does Medium Affect the Speed of Sound? The closer the particles, the faster the vibrations, the faster the sound waves travel. Sound travels fastest in solids, then liquids, and slowest in gases. The closer the particles, the faster the vibrations, the faster the sound waves travel. Sound travels fastest in solids, then liquids, and slowest in gases. 9/7/20156

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? 9/7/20157

Changing the Speed: How the Hindenburg disaster really sounded DmXvXcbk&safety_mode=true&persist _safety_mode=1&safe=activehttp:// DmXvXcbk&safety_mode=true&persist _safety_mode=1&safe=active DmXvXcbk&safety_mode=true&persist _safety_mode=1&safe=activehttp:// DmXvXcbk&safety_mode=true&persist _safety_mode=1&safe=active 9/7/20158

Properties 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.) 9/7/20159

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.) The “highness” or “lowness” of sound is the pitch. Pitch depends on the frequency of the sound waves (1 Hz = 1 wave per sec.) 9/7/201510

Frequency and Human Hearing Humans can hear frequencies between 20 Hz and 20,000 Hz (depends on age). Just like any machinery, parts become worn with age. As humans mature, they may need more amplification of sound vibrations (hearing aids) Humans can hear frequencies between 20 Hz and 20,000 Hz (depends on age). Just like any machinery, parts become worn with age. As humans mature, they may need more amplification of sound vibrations (hearing aids) 9/7/201511

Pitch and Frequency of Sound Infrasonic – Sounds with frequencies lower than 20 Hz (outside of range of human hearing) Some animals communicate this way. 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) Some animals communicate this way. Ultrasonic – Sounds with frequencies greater than 20,000 Hz (Too high for hearing, can be used for cleaning jewelry.) 9/7/201512

Vocal Cord Vibration Changes Causes Pitch Changes Helium and Sulfur hexafluoride: 3cB4YJg&safety_mode=true&persist_s afety_mode=1&safe=activehttp:// 3cB4YJg&safety_mode=true&persist_s afety_mode=1&safe=active Helium and Sulfur hexafluoride: 3cB4YJg&safety_mode=true&persist_s afety_mode=1&safe=activehttp:// 3cB4YJg&safety_mode=true&persist_s afety_mode=1&safe=active 9/7/201513

Ultrasound 9/7/ Hear the reaction of a couple who find out they are having twins! =1EStMIHpFow&safety_mode=tru e&persist_safety_mode=1

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. In sound, when you increase the amplitude of a wave, you increase the loudness of that wave. Loudness is measured in decibels. 9/7/201515

How Loud Can You Hear? 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. 9/7/201516

Common Noises and Their Decibel Levels 9/7/ 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.

The Doppler Effect The Doppler Effect is a change in sound caused 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 caused 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? 9/7/201518

Transferring Sound to Paper Sound waves can be received and then graphed on paper. The instrument that can do this is called an oscilloscope. 9/7/201519

Interactions 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. 9/7/201520

Dolphin Using Echolocation 3jaeNC4&safety_mode=true&persist_sa fety_mode=1http:// 3jaeNC4&safety_mode=true&persist_sa fety_mode=1 3jaeNC4&safety_mode=true&persist_sa fety_mode=1http:// 3jaeNC4&safety_mode=true&persist_sa fety_mode=1 9/7/201521

Can Humans Use Echo Location? RRwu5Gwhttp:// RRwu5Gw RRwu5Gwhttp:// RRwu5Gw 9/7/201522

The 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. 9/7/201523

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. ature=related&safety_mode=true&persist_safety_mo de=1&safe=activehttp:// ature=related&safety_mode=true&persist_safety_mo de=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. ature=related&safety_mode=true&persist_safety_mo de=1&safe=activehttp:// ature=related&safety_mode=true&persist_safety_mo de=1&safe=active 9/7/201524

Light and Sound: The Russian Meteor of February, 2013 Once a meteor enters our atmosphere, the amount of friction causes both intense light and heat. The momentum of the meteor is faster than the speed of sound. Go_ZmU Once a meteor enters our atmosphere, the amount of friction causes both intense light and heat. The momentum of the meteor is faster than the speed of sound. Go_ZmU 9/7/201525