# Oscilloscopes and sound

An oscilloscope is a machine that shows the wave shape of an electrical signal. When connected to a microphone they can show the wave shapes of sounds. These diagrams show oscilloscope traces of three sounds:

### Sounds 1 and 2

• The sound waves have the same , so the sounds have the same .
• Sound 2 has a greater than sound 1, so sound 2 is louder.

### Sounds 2 and 3

• The sound waves have the same amplitude, so the sounds have the same loudness.
• Sound 3 has a greater frequency than sound 2, so sound 3 is higher pitched.

The frequency of a sound is the number of oscillations (waves) per second and is measured in hertz (Hz). It can be calculated by: The time period is the time taken to complete one oscillation and is measured in seconds. So if the time period of a sound wave is 0.01 seconds, then the frequency is calculated as:

frequency = 1 ÷ 0.01

= 100 hertz

This would make a low pitched sound (low frequency) as this is towards the bottom of our audible range.