SOUND

sound is a huge part of our lives.

Ranging from music, to conversation, to our pets barking or purring, sound is important. It lets us know about danger: a siren, emotions: a change in voice pitch, even where someone is from: accents.

It plays a key role in our social interaction, our education, and our safety.

Imagine a world without music or conversation...

Sound waves

Sound waves are longitudinal. They are formed by air molecules compressing (getting close) and then rarefacting (becoming distanced)

Sometimes the waves reflect: an echo. 

To louden your phone speaker, you often put it in a glass, for example, so the sound will reflect and amplify. 

MEASURING SPEED

TIME/DISTANCE = SPEED

Place two microphones 1m away from each other

Plug them into a timer that will start when microphone 1 picks up a noise and stop when microphone 2 does too.

Divide this time by 1m (the distance)

mic 1

mic 2

meter stick

timer

sound source

FREQUENCY/ PITCH

The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium

High frequency = High pitch

Low Frequency = Low Pitch

How sound moves through...

SOLIDS, LIQUIDS AND GASES? 

THE SPEED OF SOUND MOVING THROUGH A MEDIUM DEPENDS UPON HOW CLOSE ITS MOLECULES ARE: IF THE MOLECULES ARE CLOSE, THEY WILL COLLIDE FAST, AND THE SPEED OF SOUND WILL BE FAST. VICE VERSA.

SO LETS TAKE A LOOK AT SOLIDS, LIQUIDS AND GASES AT A MOLECULAR LEVEL

Solids - close, compact molecules, so they transport sound fast

Liquid - slightly less compact molecules with some space between them, transporting sound relatively fast

Gas - molecules moving freely, not at all compacted, meaning sound takes a while to transport through gas 

My examples

1. Tapping a pen on the table - the contact of the table and the pen make the air around the contact point vibrate out

2. Keys jangling - when they make contact and smash together, the air around them vibrates out, again reaching your ears

3. Whistling - My lips are forcing out air which is vibrating against my lips and mouth, but most importantly in the air to produce a sound. These vibrations travel through air, to your ear.

hertz 

Pen on Table (80Hz) - slower vibration, low frequency, low pitch

Keys (130Hz) - slightly faster vibration, still low frequency, average pitch

Whistling (3500Hz)- fast vibration, high frequency, high pitch

LET'S SEE WHAT YOU LEARNT with a game

Fun Fact: the background is a from a sound imaging device, an ultrasound, using sonography

Match the noise/song with its frequency

1-b

2-E

3-A

4-C

5-D

Thank you