Lesson 3 — 5.2 The ear + Intro 5.3 Decibel scale

• Science
• Middelbare school
• havo
• Leerjaar 2

Chapter 5

Sound

§5.2 Detecting sound

+

§5.3 Loudness

This lesson

•  Decibel scale — Intro
• Recap
• §5.2 Detecting sound
• §5.3 Loudness

The decibel

• the unit of sound intensity
• Symbol — dB.
• Invented in 1920 by New York telephone engineers.

Decibel meter

Recap

What did we cover previous lesson?

Learning goals

• Recap — You know the difference between transverse and longitudinal waves. You also know what compression and rarefaction are.

• You can name the three main sections of the ear and their function.
• You can explain how a microphone works.
•  You can explain how the decibel scale works.
• You can read the decibel scale.

1)How is sound produced?

2) What is a medium?

3) Explain what is meant by 

• a) Compression
  
• b) rarefaction
  

4) Longitudinal waves, transverse waves

• a) How are they different?
• b) What do they have in common?

How is sound produced?

• Through a vibration

What is sound made off?

• Sound waves
  

How does sound travel over distance?

• Through a medium
  

Paragraph 5.2

Detecting sounds

Outer ear

• Collect sounds waves, channels them to the middle ear
  
• Also dampens the sound.

Middle ear

•  Amplifies the sound waves
• Channels the vibration to the inner ear

Inner ear

• Turns the wave pattern into an electric signal so that it can be send to the brain through nerves

Can you find the pattern?

• Office noise — Heavy traffic: 10 times louders
• Office noise — Subway, shouted conversation: 100 times louder
• Office noise —  School dance: ... times louder

Can you find the pattern?

• Office noise — Heavy traffic: 10 times louders
• Office noise — Subway, shouted conversation: 100 times louder
• Office noise —  School dance: 1000 times louder

Question

a) Two people are investigating sound intensity levels in decibel. One of them measures background music to have a sound intensity of 60 dB.  The other one measures a busy subway station to have a sound intensity of 90 dB. How much louder is a busy subway compared to background music?

Later they measure leaves rustling to have a sound intensity of 30 dB. Another sound source they measure makes sound that is 100 times louder. A third sound source they measure makes a sound that is 10.000 times louder. 

b) what was the second sound source they measured?

c) What was the third sound source they measured?

Homework

§5.3 – All the workbook exercises, including exercise E

Learning goals

• Recap — You know the difference between transverse and longitudinal waves. You also know what compression and rarefaction are.

• You can name the three main sections of the ear and their function.
• You can explain how a microphone works.
•  You can explain how the decibel scale works.
• You can read the decibel scale.