Physics of sound

Loudness Pitch

Anatomy of our ears

How are sound produced?

10 second activity: 1. Make an “aaahhhhh” sound, meanwhile,

place your hand on the front of your throat2. Can you feel vibrations?

• Sounds are produced by VIBRATIONS

• When things vibrate, they move backwards and forwards very rapidly

• Musical instruments produce sounds in the similar manner

How does sound travel?

• Sound requires a MEDIUM to travel• Cannot travel through vacuum

Sound travels through solids

Sound travels through liquids

Sound travels through gases

Place your ear on one end of a table and tap the table.Can you hear?

Aquatic animals like dolphins make sound underwater

We can hear each other in air.

Speed of sound

• Sound travels at about 330 m/s in air.• It can travel faster in liquids and solids.

Supersonic jets

They travel faster than speed of soundSince Concorde's final retirement flight on November 26, 2003, there are no supersonic passenger aircraft left in service

How do we hear sounds?

• Sound travels in the form of WAVES• We cannot SEE sound waves, but we can

detect them when they reach our ears.

• The waves in the air are formed from VIBRATING AIR MOLECULES. In this way, energy is passed from molecule to molecule until it reaches our ears.

Anatomy of ears

• There are three important parts of our ear• Outer ear (collect sound waves)• Ear drum (between outer and middle ear)• Middle ear (contains ear bones which magnify

the vibrations and pass them to inner ear)• Inner ear (auditory nerves in inner ear detect

vibrations and change them into electrical signals, to be carried to the brain)

Anatomy of ear (picture)

Ear bones

Ear drum

Auditory nerve

Outer ear Middle ear

inner ear

Range of hearing

• Human ears has limited hearing range of sound frequencies (pitch)

• We can only hear between 20 Hz -20 000 Hz

• Mosquito tone: very close to 20 000 Hz• Animals have other ranges.

Rat repellent

Sms ring tone that parents and teachers cant hear!

Range of hearing of animals• Frog: 50 Hz – 10 000 Hz (lower than human)• Cat: 45 Hz – 64 000 Hz (higher than human)• Elephant: 15 – 12 000 Hz

Sound and music

• The highness and lowness of a musical note is called its FREQUENCY

• High pitch: high frequency• Low pitch: low frequency• Frequency is measured in Hertz (Hz)

Loudness and softness

• Sounds can be loud or soft• Loud sound has more energy than soft sound• Loudness depends on the size of vibrations• Large vibration large amplitude• Small vibration small amplitude

Amplitude