Edexcel iGCSE Physics -3.28P Pitch and Frequency- Study Notes- New Syllabus

Pitch and Frequency of Sound

Pitch describes how high or low a sound is perceived by the human ear. The pitch of a sound is determined by the frequency of vibration of the sound source.

Frequency and Pitch

Frequency is the number of vibrations or oscillations produced per second and is measured in hertz (Hz).

• High frequency → high pitch
• Low frequency → low pitch

The pitch of a sound increases as the frequency of vibration increases.

Source of Sound

• Sound is produced by vibrating objects.
• Faster vibrations produce higher frequency sounds.
• Slower vibrations produce lower frequency sounds.

For example, a tightly stretched string vibrates faster than a loose string.

Wave Relationship

Sound waves obey the wave equation:

\( \mathrm{v = f\lambda} \)

• For sound in air, the speed \( \mathrm{v} \) is approximately constant.
• As frequency increases, wavelength decreases.

Important Distinction

• Pitch depends on frequency.
• Loudness depends on amplitude.
• Changing amplitude does not change pitch.

Key Idea

• Pitch is a perception of frequency.
• Frequency is a physical quantity.
• Higher frequency sounds are heard as higher pitch.

Important Points to Remember

• Pitch is measured qualitatively (high/low).
• Frequency is measured quantitatively in hertz.
• The frequency is set by the vibrating source.