Sound Is A Wave

Sect. 16-1

3 Min. Warm-up In each situation below, what

might happen to show that the waves transfer energy? a seaside beach in a storm an earthquake movement of coils

3 Min. Warm-up In each situation below, what

might happen to show that the waves transfer energy? a seaside beach in a storm : waves in

the water eroding the beach an earthquake : waves in the earth

shaking buildings movement of coils: a wave traveling

from one end to the other

Sound

A wave produced by a vibrating object that travels through a gas, liquid, or solid.

Longitudinal or compression wave Mechanical wave Transfers kinetic energy through a

medium (between particles by compressing them)

Explore Sound What is sound? What did you hear when the spoon

tapped the desk? How did sound travel from the

spoon to your ears?

Sound is a type of mechanical wave. Why?

Sound is a type of mechanical wave. Why?

It transfers energy through a medium.

It is produced by a vibrating object and travels through matter

The disturbances that travel in a sound wave are vibrations.

Vibration

A rapid, back and forth motion

How Sound Waves Are Produced?

Say “aahh” and place your fingers on your vocal cords.

What do you feel?

How Sound Waves Are Produced?

Sound waves are produced by vibrations that are usually too small to see. The vibrations push and pull on the medium around them and send waves out in all directions. The vocal cords are a sound-making instrument in the human body.

Your vocal cords are tensed up when you are about to speak or sing.

Vocal cords are relaxed when you are breathing, to allow air to pass in and out of your wind pipe.

How Sound Waves Are Detected1. Sound waves reaches outer ear2. The outer ear collects the waves and

sends them to the ear canal where they are received by eardrum.

3. The eardrum begins to vibrate; The middle ear carries vibrations to the inner ear

4. The inner ear sends signal to the brain

How Sound Waves Are Detected

How Sound Waves Are Detected

What effect would an inner ear infection, when the inner ear fills up with fluid, have on hearing?

What effect would an inner ear infection, when the inner ear fills up with fluid, have on hearing?

Most ear infections block some vibrations from passing through the inner ear.

Sound Waves Vibrate Particles

Ex) Vibrating DrumThe vibrating drum skin

pushes against nearby air particles and compresses

them. The drum skin pushes the opposite way and opens a space between it and the air particles. The back and forth disturbance travels to

the listeners

Wave

Summarize in your own words how sound travels through the air.

Summarize in your own words how sound travels through the air.

Sound travels as compressions in the particles that make up the air.

Vacuum Empty space Has no or few particles Sound cannot travel through it.

Why Sound Cannot Travel Through a Vacuum Sound waves require particles to

move in order to travel. In a vacuum, there are no

particles, so there is nothing for a sound wave to move.

The Speed of Sound Depends On Its Medium

What factors affect the speed of sound? Material that

makes up the medium

Temperature of the medium

The Effect of the Material Why do sound waves travel fastest

through solids? Particles are closest together in solid

materials, so sound waves can pass faster from particles to particle

The Effect of the Temperature How does the temperature of the

medium affect the speed of sound? Why? The colder the temperature, the

slower sound travels because the air particles don’t move as fast when it’s cold.

Compare and Contrast Does sound travel faster through

liquids or gases?

Compare and Contrast Does sound travel faster through liquids

or gases? Sound travels faster through liquids than it

does through gases because liquids are denser than gases. That means that the particles are closer together. It takes less time for a water particle to push on the water particles around it because the particles are already closer together than are the particles in air. As a result, divers underwater would hear a sound sooner than people above the water would.

Compare and Contrast p.523

What is the difference between the speed of sound in air at 0oC and 100oC?

Effect of Temperature Sound travels faster through a medium at

higher temperatures than at lower ones. Gas particles are not held tightly together as are particles in solids. Instead, the gas particles bounce all around. The higher the temperature, the more the gas particles wiggle and bounce. It takes less time for particles that are already moving quickly to push against particles that are moving slowly. Sound, therefore, travels faster in hot air than in cold air.

Effect of Medium & Temperature Mike was hammering nails into a wall so

that he could hang pictures. Three of his friends each stood in nearby rooms that were about 60 feet away from the hammer and nail. Who could hear the sound of the hammering first: Iceman, who stood in a cold room; Sweaty Eddy, who stood in a hot room ; or Nosey Nelson, who leaned with his ear against the wall in the hot room? Who heard it second? Why?

Effect of Medium & Temperature

Iceman – cold room

Sweaty Eddy – hot room

Nosey Nelson – hot room with ear to wall.

Effect of Medium & Temperature

1. Nosey Nelson – hot room with ear to wall. (Sound travels faster in a material with higher density such as a wall

2. Sweaty Eddy – hot room (The higher the temp., the faster the speed of sound.

3. Iceman – cold room