Frequency & Pitch

• Frequency — number of vibrations per second.
• Unit hertz (Hz); determines pitch (shrill vs grave).
• Human hearing range ~20 Hz to 20,000 Hz.
• Comparison: tabla vs flute; male vs female voice.

1. Frequency (ν) — vibrations per second; unit Hz (1 Hz = 1 vibration/s).
2. Pitch — how shrill or grave a sound is; higher frequency → higher pitch.
3. Amplitude separate from pitch — loudness depends on amplitude, not frequency.
4. Diagram (text) — wave with more crests per second = higher frequency.
5. Real world — mosquito wing beat high frequency; thunder low frequency rumble.
6. Ultrasound — above 20 kHz (used in medical imaging — intro mention).

Comparing pitch of two tuning forks

Step 1 — Strike fork A — hear higher note (more vibrations/s).
Step 2 — Fork B — lower note (fewer vibrations/s).
Step 3 — Conclude: A has higher frequency → higher pitch.
Step 4 — Frequency measured with stroboscope or electronic counter in lab.

• Confusing pitch with loudness (loudness = amplitude).
• Misconception: all sounds audible to humans (ultrasound inaudible).
• Using speed instead of frequency for pitch.
• Thinking frequency has unit m/s (that's speed of wave).

• Define frequency and its SI unit.
• How does frequency relate to pitch?
• Approximate range of human hearing in Hz.

Open the Practice tab for graded questions on Frequency & Pitch.