(3.23-3.29P) Sound waves

What are sound waves?

Longitudinal waves that can be reflected and refracted.

What is the frequency range of human hearing?

20 - 20000 Hz

How and why does the density of a medium affect the speed of sound?

sound waves caused by vibrating particles

denser medium = faster travel

Describe the experiment to investigate the speed of sound in air.

1. Two people at 100m apart.

2. A bangs together blocks to make a sound.

3. B starts timer when they see the bang, stop when they hear the noise.

4. Repeat and take average for time taken.

5. Repeat for several distances.

What is an oscilloscope?

A device that displays a signal as a trace on a screen.

the longitudinal wave is displayed as a transverse wave

How can a sound wave be displayed with a microphone and an oscilloscope?

mic picks up sound waves

plugging the mic → it converts the sound waves into electrical signals

oscilloscope screen displays signals

Describe how to investigate the frequency of a wave with an oscilliscope.

1. connect mic to oscilloscope.

2. adjust time base until signal fits on screen

3. hold tuning fork near microphone and observe.

4. repeat with different forks.

The frequency of a wave can be calculated by analysing the oscilloscope trace

• the number of entire waves on screen = frequency

How does pitch relate to frequency?

higher frequency = higher pitch

lower frequency = lower pitch

How does the volume of a sound relate to amplitude?

greater amplitude = greater energy = greater sound