How Sound Travels

Sounds are carried by vibrating particles.

Sounds can travel through:

1. Gases ( air in the room )

2. Liquids ( water in a swimming pool )

3. Solids ( walls and windows )

Sounds cannot travel through a vacuum ( totally empty space ).

The Stethoscope

At the end of the stethoscope there are 2-bells.

flexible tubing

open bell (heart

sounds)

closed bell (lung

sounds)

earpieces

The open bell is used to listen to heart sounds.

The closed bell is used to listen to lung sounds.

Vibrations travel through the flexible tubing to the earpieces of the stethoscope.

When using a stethoscope, the earpieces must be a good fit to cut out any background noise.

Ultrasound

Sound waves can have different frequencies.

Humans can only hear sounds within the frequency range of 20 Hz to 20,000 Hz.

Sounds with a frequency above 20,000 Hz are called ultrasound.

Ultrasounds are used in medicine to see inside of the body, for instance to check on an unborn baby.

Ultrasound Ringtones

How Ultrasound Works

1. A gel is rubbed onto the mother’s skin (this stops the ultrasound reflecting).

2. An ultrasound transmitter sends ultrasonic waves into the mother’s womb.

3. These waves reflect off the baby and are detected using an ultrasound receiver.

4. A computer uses these waves to produce an image of the baby.

Recent developments in technology mean that ultrasound can now be used to produce 3D images of an unborn baby.

Ultrasound is also used in medicine to treat patients with kidney stones (stones which block the flow of waste material from the body).

The Process

1. Pads are attached to patient.

2. Several ultrasound beams are focussed on the stones so shockwaves are produced at a common focus.

3. Stones are shattered with no damage to surrounding tissue.

4. Small pieces of stone are then passed through in normal waste from body.

Ultrasound waves smashing a large kidney

stone into smaller fragments.

Removed kidney that had produced 4,504 kidney

stones.

Most produced was 22 stones in 24 hours.

Noise Pollution

We are surrounded by noise from the environment we live in.

A lot of this is unwanted noise, and is called noise pollution.

Some examples of noise pollution are:

• traffic noise

• building works

• aeroplanes

• noisy neighbours

Measuring Noise Level

Noise levels are measured in units called decibels ( dB ).

Some noises are so loud that they can cause permanent damage to your hearing.

Ear protectors are often worn in noisy environments to reduce the level of noise entering the ear.

A material that absorbs some of the noise is used in ear protectors.

Noise Noise Level (dB)

silence

whisper

normal conversation (at 1 metre)

telephone ringing (at 2 metres)

DANGER LEVEL

lorry from pavement

pneumatic drill at 5m

disco speaker at 1m

low flying jet at 50m

0

30

60

70

80

90

100

120

130