AGENDA Chapter 13 Notes Chapter 13 Notes United Streaming Video on Sound United Streaming Video on Sound

SOUND: one of the most simple and common kinds 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? Cochlea: tiny fluid filled organ in the inner ear. Cochlea: tiny fluid filled organ in the inner ear. Inner Ear: Provides hearing and balance Inner Ear: Provides hearing and balance The three semicircular canals are filled with fluid. Fluid moving in each canal tells the brain which way the body is moving. The three semicircular canals are filled with fluid. Fluid moving in each canal tells the brain which way the body is moving.

Cochlea  Ear drum vibrates  Three bones send vibration to Cochlea  Fluid vibrates  Waves travel up spiral  Large end = Responds to Longer wavelength and lower frequency  Small end = Responds to Shorter wavelength and higher frequency

Human Hearing Our range: 20 Hz to 20,000 Hz Our range: 20 Hz to 20,000 Hz Could not hear a sound at 50,000 Hz even if it is at 100 decibels (really loud) Could not hear a sound at 50,000 Hz even if it is at 100 decibels (really loud)

Real life Connections…. Adults: usually cannot hear above 15,000 Hz Adults: usually cannot hear above 15,000 Hz Children: can often hear up to 20,000 Hz Children: can often hear up to 20,000 Hz Lose HIGH frequency hearing with Age Lose HIGH frequency hearing with Age Loud sound for extended time: cause the tiny hair to weaken or even break off! (Musicians use earplugs when they play!!) Loud sound for extended time: cause the tiny hair to weaken or even break off! (Musicians use earplugs when they play!!) Ultrasound: (100,000 Hz) Ultrasound: (100,000 Hz) cannot hear the waves, but pass through our bodies to make images (due to refraction and reflection) cannot hear the waves, but pass through our bodies to make images (due to refraction and reflection)

What is Sound? The back and forth motion of the speaker creates alternating layers of high and low pressure. The back and forth motion of the speaker creates alternating layers of high and low pressure. The pressure waves travel away from the speakers as sound. The pressure waves travel away from the speakers as sound.

For most sounds, the amplitude of the pressure wave is very small, so it is hard to actually feel the pressure. For most sounds, the amplitude of the pressure wave is very small, so it is hard to actually feel the pressure. You can feel sound at lower frequencies (<100Hz) (larger amplitudes) (ex. Sub-woofer, loud bass guitar) You can feel sound at lower frequencies (<100Hz) (larger amplitudes) (ex. Sub-woofer, loud bass guitar) Sound waves are longitudinal (compression) waves because the air is compressed in the direction of travel. Sound waves are longitudinal (compression) waves because the air is compressed in the direction of travel.

Sound cannot travel in space!

Loudness Measured in decibels (dB) – related to amplitude. Measured in decibels (dB) – related to amplitude.

Frequency of Sound We hear the different frequencies of sound as having different pitch. We hear the different frequencies of sound as having different pitch. A low frequency sound has a low pitch. A low frequency sound has a low pitch. A high-frequency sound has a high pitch. A high-frequency sound has a high pitch. Humans can hear from ~20Hz to 20,000Hz. Humans can hear from ~20Hz to 20,000Hz.

High frequency sounds seem louder than low frequency sounds. High frequency sounds seem louder than low frequency sounds. This is because our ears are more sensitive to sounds between 100 and 2,000 hz. This is because our ears are more sensitive to sounds between 100 and 2,000 hz. Most sound we hear contains many frequencies, not just one. Most sound we hear contains many frequencies, not just one.

Sonogram Also known as an ultrasound. Also known as an ultrasound. It utilizes specialized sound waves that bounce off your internal organs to obtain images. It utilizes specialized sound waves that bounce off 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 above the range of human hearing, hence the name Ultrasound. The pitch, or frequency, of these sound waves is far above the range of human hearing, hence the name Ultrasound. An Ultrasound is given to pregnant women. An Ultrasound is given to pregnant women. This same exam can also be used to visualize certain digestive organs, such as the gallbladder, liver and pancreas as well as the main abdominal blood vessel, the aorta. This same exam can also be used to visualize certain digestive organs, such as the gallbladder, liver and pancreas as well as the main abdominal blood vessel, the aorta.

Wavelength of Sound Organ pipes are made in all different sizes to match the specific wavelengths of sound.

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

Speed Depends on Temperature and Pressure Air molecules move slower on a cold day, and travels faster on a hot day. Air molecules move slower on a cold day, and travels faster on a hot day. Air is made up of mainly oxygen and nitrogen molecules. Air is made up of mainly oxygen and nitrogen molecules. Lighter molecules like Helium (He) move faster, so sound travels faster. Lighter molecules like Helium (He) move faster, so sound travels faster.

ACOUSTICS The science and technology of sound. The science and technology of sound. Soundproofing – to stop sound we use Soundproofing – to stop sound we use Dense, thick wall materials (concrete & brick) Dense, thick wall materials (concrete & brick) Careful sealing around doors and openings to stop sound from leaking through cracks. Careful sealing around doors and openings to stop sound from leaking through cracks. Thick curtains and carpets to help absorb reflected sound on floors and walls. Thick curtains and carpets to help absorb reflected sound on floors and walls. Acoustic Tiles are used to reduce the loudness of sound reflected off the ceiling. Acoustic Tiles are used to reduce the loudness of sound reflected off the ceiling. Music studios usually have very good soundproofing. Music studios usually have very good soundproofing.

How sound waves are affected by surfaces. In a good concert hall, the reflected sound ads to the direct sound. In a good concert hall, the reflected sound ads to the direct sound. You hear a multiple echo called reverberation which (if done right) can make the sound seem livelier and richer. You hear a multiple echo called reverberation which (if done right) can make the sound seem livelier and richer. Some concert halls have Some concert halls have moveable panels that can be moveable panels that can be raised or lowered to help with sound.

Interference can also Affect Sound Quality Reverberation is a multiple echo caused by reflected sound. Reverberation can also cause interference of sound waves. Reverberation is a multiple echo caused by reflected sound. Reverberation can also cause interference of sound waves. Two waves can interfere to be louder or softer. Two waves can interfere to be louder or softer. Dead Spots in concert halls are areas where destructive interference causes some of the sound to cancel out. Dead Spots in concert halls are areas where destructive interference causes some of the sound to cancel out.

Music: Combo of Sound & Rhythm that we find pleasant Pitch: How high or low we hear its frequency (Pitch and frequency are the same)…. Can be affected by what we hear before or after. Pitch: How high or low we hear its frequency (Pitch and frequency are the same)…. Can be affected by what we hear before or after. Rhythm: Regular time pattern in sound…Can be made with sound or silence…cultures are distinguished by their unique music and rhythms. Rhythm: Regular time pattern in sound…Can be made with sound or silence…cultures are distinguished by their unique music and rhythms.

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

 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 Dissonance When we hear more than one frequency of sound and the combination is good= Consonance (used to create feelings of comfort) When we hear more than one frequency of sound and the combination is good= Consonance (used to create feelings of comfort) Usually frequencies are far enough apart or exactly the same that there are no beats. When the combination is NOT good= Dissonance (used to create tension or drama: try watching your favorite movie without the sound, not as scary!!) When the combination is NOT good= Dissonance (used to create tension or drama: try watching your favorite movie without the sound, not as scary!!) Usually frequencies are too close = beats are produced

Homework Chapter 13 Vocabulary Chapter 13 Vocabulary Chapter 13 Concept Review Chapter 13 Concept Review