Amplitude & Loudness

• Amplitude — maximum displacement of particles from rest position in a wave.
• Loudness depends on amplitude — larger amplitude → louder sound.
• Soft vs loud tabla stroke; whisper vs shout.
• Distinction from frequency (pitch).

1. Amplitude (A) — size of vibration; measured from mean to crest.
2. Loudness — sensation proportional to amplitude² (qualitative at Class 8).
3. Same frequency, different amplitude — same pitch, different loudness.
4. Diagram (text) — tall wave = loud; short wave = soft (same wavelength).
5. Real world — volume knob increases amplitude of speaker diaphragm; thunder louder than whisper.
6. Energy — louder sound carries more energy.

Tabla player hits harder vs softer (same note)

Step 1 — Same tabla skin → same frequency (pitch).
Step 2 — Harder hit → larger vibration amplitude.
Step 3 — Louder sound heard.
Step 4 — Soft hit → small amplitude → faint sound.

• Thinking louder sound always has higher pitch.
• Misconception: amplitude changes frequency.
• Confusing amplitude with wavelength.
• Believing vacuum can carry loud sounds (needs medium).

• What is amplitude?
• How does amplitude affect loudness?
• Two sounds same pitch — how can one be louder?

Open the Practice tab for graded questions on Amplitude & Loudness.