Pitch & Loudness (Edexcel IGCSE Physics)

• The pitch of a sound is related to the frequency of the vibrating source of sound waves
  • If the frequency of vibration is high, the sound wave has a high pitch
  • If the frequency of vibration is low, the sound wave has a low pitch

The relationship between the pitch and frequency of sound

The pitch of the sound is related to the frequency of the sound waves

Comparing the pitch of sound displayed on an oscilloscope

This image shows two sound waves displayed on an oscilloscope. The red wave has smaller wavelength than the blue wave hence it has higher frequency and higher pitch

• The loudness of a sound is related to the amplitude of the vibrating source of sound waves
  • If the sound is loud, the sound wave has a large amplitude

Comparing the volume of sound displayed on an oscilloscope

This image shows two sound waves displayed on an oscilloscope. The blue wave has twice the amplitude of the green wave because the blue wave is louder

• The human ear responds to the vibrations caused by sound waves
• The frequency range for human hearing is 20 Hz to 20 000 Hz
  • Below the frequencies that humans can hear is infrasound
  • Above the frequencies that humans can hear is ultrasound

The infrasound, human hearing and ultrasound frequency ranges

The range of human hearing is between 20 – 20 000 Hz. Below 20 Hz is known as infrasound. Above 20 000 Hz is known as ultrasound