Properties of Sound Waves (Cambridge (CIE) O Level Physics) : Revision Note

Pitch & Loudness

• The frequency of a sound wave is related to its pitch

  • Sounds with a high pitch have a high frequency (or short wavelength)

  • Sounds with a low pitch have a low frequency (or long wavelength)

• Sounds with a large amplitude have a high volume

  • Sounds with a small amplitude have a low volume The amplitude of a sound wave is related to its volume

Graphs of Different Amplitudes & Frequencies

The amplitude of a wave determines the volume of the sound and the frequency determines the pitch

Different Sound Sources

• An oscilloscope is a device that can be used to study a rapidly changing signal, such as:

  • A sound wave

  • An alternating current

Oscilloscope

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 time base (like the 'x-axis') is used to measure the time period of the wave

A Soundwave Depicted as a Transverse Wave 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