Sound & Oscilloscopes (Edexcel IGCSE Physics)
Revision Note
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Sound & oscilloscopes
An oscilloscope is a device that can be used to study a rapidly changing signal, such as:
A sound wave
An alternating current
An oscilloscope is used to display sound as a waveform
Oscilloscopes have lots of dials and buttons, but their main purpose is to display and measure changing signals like sound waves and alternating current
When a microphone is connected to an oscilloscope, the (longitudinal) sound wave is displayed as though it were a transverse wave on the screen
The properties of longitudinal and transverse waves are explained in the revision note Transverse & longitudinal waves
The time base (like the 'x-axis') is used to measure the time period of the wave
An explanation of the sound waveform as displayed on an oscilloscope
A sound wave is displayed as though it were a transverse wave on the screen of the oscilloscope. The time base can be used to measure a full time period of the wave cycle
The height of the wave (measured from the centre of the screen) is related to the amplitude of the sound
The number of entire waves that appear on the screen is related to the frequency of the wave
If the frequency of the sound wave increases, more waves are displayed on screen
Examiner Tips and Tricks
Take time to understand how the oscilloscope displays sound as a waveform, as it is more complicated than you think. Make sure you know what happens to the wave if you change either the horizontal or vertical axis.
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