Pitch is the brain’s perception of how high or low a sound seems, and it is closely related to the sound wave’s frequency. In music, pitch lets us tell one note from another, tune instruments, and recognize melody. The ear turns tiny pressure changes in air into electrical signals that the brain can compare and identify.
Understanding pitch connects physics, biology, and music in one system.
Key Facts
- Frequency measures cycles per second: 1 Hz = 1 cycle/s.
- Higher frequency usually means higher perceived pitch.
- Wave speed relation: v = fλ.
- For sound in air at room temperature, v ≈ 343 m/s.
- Octave relation: doubling frequency raises pitch by one octave, so f2 = 2f1.
- Sound energy is converted to nerve signals by hair cells in the cochlea.
Vocabulary
- Pitch
- Pitch is how high or low a sound is perceived by the brain.
- Frequency
- Frequency is the number of wave cycles that pass a point each second.
- Cochlea
- The cochlea is the spiral-shaped inner ear structure that converts sound vibrations into nerve signals.
- Basilar membrane
- The basilar membrane is a flexible strip inside the cochlea that vibrates at different places for different frequencies.
- Hair cell
- A hair cell is a sensory cell in the inner ear that bends with vibration and sends electrical signals to the auditory nerve.
Common Mistakes to Avoid
- Confusing pitch with loudness: pitch depends mainly on frequency, while loudness depends mainly on wave amplitude and sound intensity.
- Thinking all parts of the cochlea respond equally to every note: different locations on the basilar membrane are most sensitive to different frequencies.
- Using wavelength without considering sound speed: wavelength and frequency are linked by v = fλ, so the medium affects the relationship.
- Assuming doubling frequency makes the sound twice as loud: doubling frequency raises pitch by one octave, but loudness is controlled by amplitude and intensity.
Practice Questions
- 1 A guitar string produces a note at 220 Hz. What frequency is one octave higher?
- 2 A sound wave in air has a frequency of 686 Hz. Using v = 343 m/s, what is its wavelength?
- 3 A flute and a tuba play notes with the same loudness, but the flute sounds higher. Explain what must be different about the sound waves and how the cochlea detects that difference.