Sound SOUND

When something like a string on a guitar or violin, or a flat surface such as a drum or diaphragm in a loudspeaker, vibrates it makes a sound. The vibrating string or surface transfers kinetic energy to the air and makes it vibrate. Sound needs a medium to vibrate so that it can travel from the source. Sound will not travel through a vacuum. We hear because sound waves enter the ear and cause the eardrum to vibrate. Bones in the inner ear carry this vibration to tiny hairs in the cochlea that send a message to the brain to be interpreted. We hear a range of sounds from low to high pitch. The range of sound frequencies that we are able to hear is called the audible range.

Make a flow diagram for what happens in the ear (on your sheet)?

Sound waves can be reflected from the surface of an object. This is called an echo. Remember sound travels much slower than light. Have you heard the rule -- see a stroke of lightning, count the seconds to the thunder and you can tell how far away the thunderstorm is? The reason for this is the sound travels about a million times slower than the light. It travels at 340 metres per second. Loud sounds are produced by lots of energy. A shout is loud and is produced by lots of energy. A whisper is quiet and is produced by a small amount of energy. We can see the effects of sound represented using an oscilloscope. The number of vibrations per second is the frequency and the pitch of the sound. A piece of chalk pulled across the black board produces a high pitched sound that has a high frequency. A cow mooing produces a low pitch and low frequency sound. Sound is measured in decibels (dB). As you move further away from the same source of sound the quieter the sound gets.

What do high and low pitches/ frequencies look like on an oscillocsope?

1

The Audible Range

Some people can not hear high pitched sounds!

What could cause poor hearing?1.2.3.4.

Frequency is measured in Hertz

Label the bar chart for frequencies which animals can hear

A. BatB.C. DolphinD. DogE. Human

Loudness is measured in DecibelsHow can your sound range be damaged?

2

120,000Hz

80,000 Hz

40,000 Hz

O Hz

120dB20dB 40dB 60dB 110dB

On the amplitude wavelength mark at what noise the following would create: People talking, traffic, a rock concert, space shuttleAt which amplitude do you think ear damage will occur?