AGENDAAGENDA Chapter 13 NotesChapter 13 Notes United Streaming Video on SoundUnited Streaming Video on Sound

SOUND: one of the most SOUND: one of the most simple and common kinds simple and common kinds

of waves.of waves.How do we know it’s a wave? Sound has frequency: Heard as HIGH or LOW pitch Sound has wavelength Speed of sound= Frequency x Wavelength Resonance happens with sound. Sound can be reflected, refracted, and absorbed. Sound shows evidence of interference and diffraction.

How do we Hear?How do we Hear? Cochlea: tiny fluid Cochlea: tiny fluid

filled organ in the inner filled organ in the inner ear.ear.

Inner Ear: Provides Inner Ear: Provides hearing and balancehearing and balance

The three semicircular The three semicircular canals are filled with canals are filled with fluid. Fluid moving in fluid. Fluid moving in each canal tells the each canal tells the brain which way the brain which way the body is moving.body is moving.

CochleaCochleaEar drum vibratesThree bones send vibration to CochleaFluid vibratesWaves travel up spiralLarge end = Responds to Longer wavelength and lower frequencySmall end = Responds to Shorter wavelength and higher frequency

Human HearingHuman Hearing Our range: 20 Hz to Our range: 20 Hz to

20,000 Hz20,000 Hz Could not hear a sound at Could not hear a sound at

50,000 Hz even if it is at 50,000 Hz even if it is at 100 decibels (really loud)100 decibels (really loud)

Real life Connections….Real life Connections…. Adults: usually cannot hear above 15,000 HzAdults: usually cannot hear above 15,000 Hz

Children: can often hear up to 20,000 HzChildren: can often hear up to 20,000 Hz

Lose HIGH frequency hearing with AgeLose HIGH frequency hearing with Age

Loud sound for extended time: cause the tiny hair to weaken Loud sound for extended time: cause the tiny hair to weaken or even break off! (Musicians use earplugs when they or even break off! (Musicians use earplugs when they play!!)play!!)

Ultrasound: (100,000 Hz)Ultrasound: (100,000 Hz) cannot hear the waves, but pass through our bodies to make cannot hear the waves, but pass through our bodies to make

images (due to refraction and reflection)images (due to refraction and reflection)

What is Sound?What is Sound? The back and forth motion of The back and forth motion of

the speaker creates alternating the speaker creates alternating layers of high and low layers of high and low pressure.pressure.

The pressure waves travel The pressure waves travel away from the speakers as away from the speakers as sound.sound.

For most sounds, the amplitude of the pressure For most sounds, the amplitude of the pressure wave is very small, so it is hard to actually feel wave is very small, so it is hard to actually feel the pressure.the pressure.

You can feel sound at lower frequencies You can feel sound at lower frequencies (<100Hz) (larger amplitudes) (ex. Sub-woofer, (<100Hz) (larger amplitudes) (ex. Sub-woofer, loud bass guitar)loud bass guitar)

Sound waves are Sound waves are longitudinal longitudinal (compression)(compression) waves because the air is waves because the air is compressed in the direction of travel.compressed in the direction of travel.

Sound Sound cannot cannot

travel in travel in space!space!

LoudnessLoudness Measured in decibels (dB) – related to Measured in decibels (dB) – related to

amplitude.amplitude.

Frequency of SoundFrequency of Sound We hear the different frequencies We hear the different frequencies

of sound as having different of sound as having different pitchpitch..

A low frequency sound has a low A low frequency sound has a low pitch.pitch.

A high-frequency sound has a high A high-frequency sound has a high pitch.pitch.

Humans can hear from ~20Hz to Humans can hear from ~20Hz to 20,000Hz.20,000Hz.

High frequency sounds seem louder than High frequency sounds seem louder than low frequency sounds.low frequency sounds.

This is because our ears are more sensitive This is because our ears are more sensitive to sounds between 100 and 2,000 hz. to sounds between 100 and 2,000 hz.

Most sound we hear contains many Most sound we hear contains many frequencies, not just one.frequencies, not just one.

SonogramSonogram Also known as an ultrasound.Also known as an ultrasound. It utilizes specialized sound waves that bounce off It utilizes specialized sound waves that bounce off

your internal organs to obtain images.your internal organs to obtain images. A submarine uses sonar to locate the enemy. A submarine uses sonar to locate the enemy. The pitch, or frequency, of these sound waves is far The pitch, or frequency, of these sound waves is far

above the range of human hearing, hence the name above the range of human hearing, hence the name Ultrasound.Ultrasound.

An Ultrasound is given to pregnant women. An Ultrasound is given to pregnant women. This same exam can also be used to visualize This same exam can also be used to visualize

certain digestive organs, such as the gallbladder, certain digestive organs, such as the gallbladder, liver and pancreas as well as the main abdominal liver and pancreas as well as the main abdominal blood vessel, the aorta. blood vessel, the aorta.

Wavelength of Wavelength of SoundSound

Organ pipes are made in all different sizes to match the specific wavelengths

of sound.

Speed of SoundSpeed of Sound Sound is fast, about 340 m/s (660 mph)Sound is fast, about 340 m/s (660 mph) Ordinary passenger jets fly ~400-500 mph.Ordinary passenger jets fly ~400-500 mph. SupersonicSupersonic is faster than sound. is faster than sound.

Speed Depends on Speed Depends on Temperature and Temperature and

PressurePressure Air molecules move slower Air molecules move slower

on a cold day, and travels on a cold day, and travels faster on a hot day.faster on a hot day.

Air is made up of mainly Air is made up of mainly oxygen and nitrogen oxygen and nitrogen molecules.molecules.

Lighter molecules like Lighter molecules like Helium (He) move faster, so Helium (He) move faster, so sound travels faster.sound travels faster.

ACOUSTICSACOUSTICS The science and technology of sound.The science and technology of sound. SoundproofingSoundproofing – to stop sound we use – to stop sound we use

Dense, thick wall materials (concrete & Dense, thick wall materials (concrete & brick)brick)

Careful sealing around doors and openings Careful sealing around doors and openings to stop sound from leaking through cracks.to stop sound from leaking through cracks.

Thick curtains and carpets to help absorb Thick curtains and carpets to help absorb reflected sound on floors and walls.reflected sound on floors and walls.

Acoustic TilesAcoustic Tiles are used to reduce the are used to reduce the loudness of sound reflected off the loudness of sound reflected off the ceiling.ceiling.

Music studios usually have very good Music studios usually have very good soundproofing.soundproofing.

How sound waves are How sound waves are affected by surfaces.affected by surfaces.

In a good concert hall, the reflected sound ads to the In a good concert hall, the reflected sound ads to the direct sound.direct sound.

You hear a multiple echo called You hear a multiple echo called reverberationreverberation which (if done right) can make the sound seem which (if done right) can make the sound seem livelier and richer.livelier and richer.

Some concert halls haveSome concert halls have

moveable panels that can bemoveable panels that can be

raised or lowered to help raised or lowered to help

with sound.with sound.

Interference can also Interference can also Affect Sound QualityAffect Sound Quality

Reverberation is a multiple echo caused by Reverberation is a multiple echo caused by reflected sound. Reverberation can also reflected sound. Reverberation can also cause interference of sound waves.cause interference of sound waves.

Two waves can interfere to be louder or Two waves can interfere to be louder or softer.softer.

Dead SpotsDead Spots in concert halls are areas where in concert halls are areas where destructive interference causes some of the destructive interference causes some of the sound to cancel out.sound to cancel out.

Music: Combo of Sound & Music: Combo of Sound & Rhythm that we find Rhythm that we find

pleasantpleasant Pitch:Pitch: How high or low we hear its frequency How high or low we hear its frequency

(Pitch and frequency are the same)…. Can be (Pitch and frequency are the same)…. Can be affected by what we hear before or after.affected by what we hear before or after.

Rhythm:Rhythm: Regular time pattern in sound…Can be Regular time pattern in sound…Can be made with sound or silence…cultures are made with sound or silence…cultures are distinguished by their unique music and rhythms.distinguished by their unique music and rhythms.

Musical Scale: Musical Scale: made from a specific set of made from a specific set of frequenciesfrequencies

Harmony: the study of how sounds combine to create effects desired by the composer.

Beats: phase of two waves changes in a way that makes the loudness of the sound seem to oscillate.

Consonance and DissonanceConsonance and Dissonance When we hear more than one frequency of sound and When we hear more than one frequency of sound and

the combination is good= the combination is good= ConsonanceConsonance (used to (used to create feelings of comfort)create feelings of comfort)

Usually frequencies are far enough apart or exactly the Usually frequencies are far enough apart or exactly the same that there are no beats.same that there are no beats.

When the combination is When the combination is NOT NOT good= good= DissonanceDissonance (used to create tension or drama: try watching your favorite (used to create tension or drama: try watching your favorite movie without the sound, not as scary!!)movie without the sound, not as scary!!)

Usually frequencies are too close = beats are producedUsually frequencies are too close = beats are produced

HomeworkHomework

Chapter 13 VocabularyChapter 13 Vocabulary

Chapter 13 Concept ReviewChapter 13 Concept Review