Waves we can hear

The source of all sound waves is

Vibration

Strings in instrumentsDrumhead in drumVocal chords in your throat

Opening and closing a door

The vibration sets the surrounding air molecules in motion

The frequency of a sound wave is the same frequency as the vibrating source

Sound travels as a longitudinal wave through the air to your ear

Compression Rarefaction

Wavelength

Wave Motion

Wavelength: Distance between two compressions

Frequency (vibrations per second)◦Perceived as PITCH Low Frequency = low pitch High Frequency = high pitch

Amplitude: Perceived as LOUDNESS Large amplitude = loud sound Small amplitude = soft sound

1. Loud & low-pitched2. Soft & high-pitched3. Medium-loud and high-pitched

4. Loud & high-pitched5. Soft & low-pitched6. Medium-loud and medium-pitched

1. Loud & low-pitched E2. Soft & high-pitched B3. Medium-loud and high-pitched C

4. Loud & high-pitched F5. Soft & low-pitched D6. Medium-loud and medium-

pitched A

Sound can only travel through matter SOLID –

◦Putting your ear to a door or wall (better if you use a glass)

LIQUIDS – ◦Dolphins communicating in water

GAS – ◦Talking

Rumble, rumble, rumble

Rumble, rumble, rumble

There’s no sound in space!Sound cannot travel in a vacuum where there is no matter

Speed of Sound at room temperature◦ 340 m/s◦ Light travels at 300,000,000 m/s◦ Sound is a million times slower than light

Speed depends on the temperature and elasticity of the medium

Elasticity◦ Ability to change shape then return to initial

shape quickly◦ Steel is elastic◦ Putty is inelastic

Atoms in elastic materials are relatively close together and respond quickly to each other’s motion

Sound travels fastest in :◦SOLID LIQUID GASES

Examples:◦Sound in steel 15 times faster than air

◦Sound in water 4 times faster than air

ExampleIf you put your ear to the ground you can hear distant horses before you could hear them through the air

Speed of sound INCREASES as temperature INCREASES◦ Molecules moving faster bump into each

other more often. Amplitude (Loudness) and frequency

(Pitch) DO NOT affect speed of sound Sonic Booms

◦ Occur when objects travels as fast as the speed of sound.