Decibels don't add up the way you'd expect. A jump from 70 dB to 80 dB isn't "a little louder" — it's a real jump in intensity, even though it only sounds roughly twice as loud.
🧭 Plot Summary
A sound wave has two physical properties you already know: frequency and amplitude. What you actually experience are two different things: pitch (how high or low a sound seems) and loudness (how big it feels). They're related, but they aren't the same words for the same thing — the wave is the physics, pitch and loudness are what your brain does with it.
Higher frequency generally means higher pitch, and bigger amplitude generally means louder — but human hearing has real limits (roughly 20 Hz to 20,000 Hz), and loudness is measured on a strange, logarithmic scale (decibels) where the numbers don't behave the way you'd guess.
What you will do in this lesson
- Split frequency from pitch, and amplitude from loudness — the wave's physical properties versus what your ear reports.
- Find the edges of human hearing, and meet infrasound and ultrasound on either side of it.
- Discover that the decibel scale is logarithmic — and why that means huge physical changes can 'sound' small.
- Use a rule of thumb to translate decibel differences into how much louder something actually feels.
- Build the perceptual vocabulary Project 3-1-3 and Problem 3-2-1 both assume you already have.
Why it matters
Project 3-1-3: Garage Band is all about pitch — tuning a homemade instrument means adjusting frequency until it sounds right. Problem 3-2-1: Band Room Bleed is all about loudness — you can't diagnose a noise complaint without decibels.
✅ Self-Check Before You Roll On
Check off each item as you get there. These are not grades — they are your own signal.