Section 1

All sounds are created by vibrations. A vibration is the complete back-and-forth motion of an object or material.

The next slide shows how a stereo speaker produces sound.

Compression

Rarefaction

Sound Waves are longitudinal waves that are caused by vibrations, which are then carried through a substance and transfers energy.

The particles of the substance vibrate back and forth along the path that the sound waves travel.

One sound wave is one complete compression and one complete rarefaction

Sound is transmitted through the vibrations and collisions of the particles.

Sound waves travel in all directions away from their source.

The air or other matter through which the wave is traveling does not travel with the sound waves. The particles of air only vibrate back and forth.

All sound waves require a medium (plural, media).

There are no particles to vibrate in a vacuum. No sound can be made in Space

All sound waves require a medium (plural, media).

Your ears are divided into three regions: the outer ear, the middle ear, and the inner ear.

The outer ear collects sound waves. Then, organs in the middle ear increase the size of the sound wave’s vibrations. The inner ear changes the vibrations into electrical signals that your brain interprets as sound.

Ear parts

Section 2

Section 2 Properties of sound

Making sound is separate from hearing sound. Sound can be made and not be heard.

E.g..: Tree in forest

The parts of the ear must work together for you to hear. If any part of the ear is damaged or does not work properly, hearing loss or deafness may result.

Loud sounds can cause damage the cochlea. Damage to the cochlea or any other part of the inner ear usually results in permanent hearing loss.

There are some simple ways to protect your hearing.

They include:

The speed of sound depends only on the medium in which the sound is traveling.

How the Speed of Sound Can Change:

SLG

Mediums:

Temperature:

Hot:

Cold:

How low or high a sound seems to be is the pitch of that sound. The pitch of a sound is related to the frequency of the sound wave.

Sound that have a frequency too high for people to hear are called ultrasonic.

High frequency waves have high pitches (Dog whistles).

Low frequency waves have _____ pitches

Pitch is related to: frequency, (Hz), and wave speed!

Sound

Speed Pitch Loudness

Properties of sound:

Doppler effect:

Happens when there is motion b/t the sound and its receiver. Think of sirens. As a siren comes toward you, the pitch of the siren was higher. After the siren passes you, the sound of the siren was lower as it moved away from you.

Louder sounds have more energy. The amplitude of sounds increases as the energy of the vibrations that caused the sound increases.

Loudness is measured in Decibles (dB). Long term exposure to 85 dB or more can cause permanent damage to hearing. Sounds over 85dB can harm faster!

Oscilloscopes turn sound into electrical signals and graphs the signal.

Interaction of sound waves:Interaction of sound waves:

Q: why are echoes impt to Q: why are echoes impt to whales?whales?

Q:Q:What kind of a surface is the best reflector of sound?

The use of reflected sounds by animals such as bats to find objects is called….

Q:How does the Doppler effect how bats find food?

When two or more waves combine to form a single wave,___________

occurs.

Sound interference:Sound interference:

Constructive =Constructive =

Destructive =Destructive =

When a jet flies at supersonic speeds…

A tuning fork cause a guitar string to vibrate without touching it by…Q: How does a guitar use resonance to make sound?

Sound qualitySound quality

Q: What is the difference between music and sound?

Q:Why do the same notes sound different on different instruments?

The result of several pitches mixing together through interference is…

Q: A sound that consists of a random mix of frequencies is a(n)