Sound Chapter 21

How Sounds are Made Sounds are vibrations that travel in longitudinal wavesSounds are vibrations that travel in longitudinal waves A vibration is the complete back and forth motion of an objectA vibration is the complete back and forth motion of an object At the crest of each wave is a compression of the molecules of the mediumAt the crest of each wave is a compression of the molecules of the medium At the trough is a rarefaction of the molecules of the mediumAt the trough is a rarefaction of the molecules of the medium

Seeing Sound

Sound and Media Medium is the substance that the sound wave travels throughMedium is the substance that the sound wave travels through Fastest in solids, then liquids, then gases.Fastest in solids, then liquids, then gases. Why?Why? Space is a vacuum, with no matter to carry the sound wave, so no sound is heard from space.Space is a vacuum, with no matter to carry the sound wave, so no sound is heard from space.

How You Hear

A is the pinna which collects the sound waves. It is the beginning of the outer earA is the pinna which collects the sound waves. It is the beginning of the outer ear B is the ear canal which directs the sound waves to the ear drumB is the ear canal which directs the sound waves to the ear drum C is the ear drum which vibrates and sends the vibrations into the middle earC is the ear drum which vibrates and sends the vibrations into the middle ear D contains the hammer, anvil, and stirrup, which are 3 small bones that vibrate and send the vibrations to the inner earD contains the hammer, anvil, and stirrup, which are 3 small bones that vibrate and send the vibrations to the inner ear E is the cochlea which is snail shaped and contains a liquid and hundreds of nerves cells which change the vibrations into nerve impulses that are sent to the brainE is the cochlea which is snail shaped and contains a liquid and hundreds of nerves cells which change the vibrations into nerve impulses that are sent to the brain

»Threshold of Hearing 0dB Normal Breathing0dB Normal Breathing 10dB Rustling Leaves10dB Rustling Leaves 20dB20dB 30dB Library30dB Library 40dB40dB 50dBNormal Conversation50dBNormal Conversation 60dB60dB 70dB Noisy Office with machines70dB Noisy Office with machines 80dB Heavy Traffic80dB Heavy Traffic 90dB90dB 100dBConstruction Noise (up close)100dBConstruction Noise (up close) 110dB110dB »Threshold of Pain 120dB Rock Concert120dB Rock Concert 130dB130dB 140dBJet Takeoff (from runway)140dBJet Takeoff (from runway) 150dB150dB

Human Hearing Infrasonic – sounds 0-20 hz to low for humans to hearInfrasonic – sounds 0-20 hz to low for humans to hear Ultrasonic - sounds greater than 20,000 hz to high for humans to hearUltrasonic - sounds greater than 20,000 hz to high for humans to hear Most humans can hear 20-20,000 hz most of their lives.Most humans can hear 20-20,000 hz most of their lives.

Hearing Loss and Deafness The most common type of hearing loss is called tinnitus, caused by exposure to loud sounds or musicThe most common type of hearing loss is called tinnitus, caused by exposure to loud sounds or music How to prevent it? Turn your I-pods down!!!!!!How to prevent it? Turn your I-pods down!!!!!! Protect your hearing by wearing ear protectors if you know you are going to be exposed to loud noise.Protect your hearing by wearing ear protectors if you know you are going to be exposed to loud noise.

Speed of Sound The speed of sound is determined by the temperature, elasticity, and density of the medium through which the sound travelsThe speed of sound is determined by the temperature, elasticity, and density of the medium through which the sound travels

Temperature Sound travels faster at higher temperatures and slower at lower temperatures due to the molecules of the mediumSound travels faster at higher temperatures and slower at lower temperatures due to the molecules of the medium Air at 0° 331 m/secAir at 0° 331 m/sec Air at 25° 346 m/secAir at 25° 346 m/sec

Elasticity and Density Solids are more elastic than either liquids or gases, the medium returns to its original position ex. Running on pavement or sandSolids are more elastic than either liquids or gases, the medium returns to its original position ex. Running on pavement or sand Sound travels best in solids, then liquids, and worst in gases because the molecules are closer together in solidsSound travels best in solids, then liquids, and worst in gases because the molecules are closer together in solids

Frequency and Pitch The description of a sound as either high or low is its pitchThe description of a sound as either high or low is its pitch The pitch depends on the frequency of a soundThe pitch depends on the frequency of a sound High frequency=high pitch low frequency=low pitchHigh frequency=high pitch low frequency=low pitch Ultrasonic higher than 20,000 hertz humans cannot hearUltrasonic higher than 20,000 hertz humans cannot hear Unfrasonic lower that 20 hertz humans cannot hearUnfrasonic lower that 20 hertz humans cannot hear

Pitch

Doppler Effect The change in pitch due to the movement between the sound and the receiverThe change in pitch due to the movement between the sound and the receiver Coming toward the receiver the sound waves are pushed togetherComing toward the receiver the sound waves are pushed together Moving away the sound waves have more space between themMoving away the sound waves have more space between them

Intensity and Loudness Intensity determines the loudness of a soundIntensity determines the loudness of a sound Intensity is the amount of energy carried in a wave in a certain amount of timeIntensity is the amount of energy carried in a wave in a certain amount of time The larger the amplitude the greater the intensity of a waveThe larger the amplitude the greater the intensity of a wave

Reflection of Sound Waves Reflection of sound waves is called an echoReflection of sound waves is called an echo EcholocationEcholocation

Sonar High frequency ultra-sonic waves are used in a system called Sound Navigation And Ranging or sonarHigh frequency ultra-sonic waves are used in a system called Sound Navigation And Ranging or sonar

Ultrasounds Ultrasonic waves are directed into a body and the resulting picture can be seen from the deflected wavesUltrasonic waves are directed into a body and the resulting picture can be seen from the deflected waves ?v=opCo2xZ9W8I&feature=rel atedhttp:// ?v=opCo2xZ9W8I&feature=rel ated

Combining Sounds When sound waves combine in such a way that the resulting disturbance is greater then either wave alone, constructive interference occursWhen sound waves combine in such a way that the resulting disturbance is greater then either wave alone, constructive interference occurs When constructive interference occurs the resulting sound gets louderWhen constructive interference occurs the resulting sound gets louder Acoustics is the science of sound, acoustic engineers design auditoriums to eliminate interference problemsAcoustics is the science of sound, acoustic engineers design auditoriums to eliminate interference problems

Destructive interference results when two sound waves combine and the resulting sound is less that the two original soundsDestructive interference results when two sound waves combine and the resulting sound is less that the two original sounds The sound gets softerThe sound gets softer

Constructive Destructive Constructive Destructive Interference Interference Interference Interference

Sonic Boom

Standing Wave A pattern of vibration that looks like the wave is standing still.A pattern of vibration that looks like the wave is standing still.

Resonance Natural vibration frequencyNatural vibration frequency

Beats Two waves of slightly different frequencies overlap, adding together in some areas, canceling each other in others. The bulges of loud sound (high wave) are called beats.Two waves of slightly different frequencies overlap, adding together in some areas, canceling each other in others. The bulges of loud sound (high wave) are called beats.

Sound Quality Musical instruments have different sound quality also known as timbreMusical instruments have different sound quality also known as timbre Each object vibrates at several different frequencies, with different pitches, the blending gives it its timbreEach object vibrates at several different frequencies, with different pitches, the blending gives it its timbre The lowest is its fundamental tone and the highest are overtonesThe lowest is its fundamental tone and the highest are overtones The blending of the fundamental tone and the overtones produces the characteristic quality or timbre of a particular soundThe blending of the fundamental tone and the overtones produces the characteristic quality or timbre of a particular sound

Music A sound is music if it has a pleasing quality, a definite identifiable pitch, and a repeating timing called rhythmA sound is music if it has a pleasing quality, a definite identifiable pitch, and a repeating timing called rhythm Noise has no pleasing quality, no identifiable pitch, and no definite relationship between the fundamental tone and the overtonesNoise has no pleasing quality, no identifiable pitch, and no definite relationship between the fundamental tone and the overtones

Heard enough?