Lesson 5 — 2B

• Science
• Middelbare school
• vwo
• Leerjaar 2

Sound

Q1) What is the wavelength of this wave?

One block is 2 cm long

Q2) What is the amplitude of this wave?

One block is 2 cm long

Q3) What is the frequency of this wave?

1 second

This lesson

• The distinct sound of instruments
• Simple sound calculations
• Echoes
  
• Echolocation
• Echo calculations
• Traveling faster than sound
  

Learning goals

• Explain how instruments get their distinct sound.
• Be able to do calculations on the speed of sound in different circumstances.
• Be able to calculate wave speed.
• Explain in your own words how echoes work.
• Describe how echo location works.
• Be able to do calculations involving echoes and echo location
• Explain how the mach system works.

The distinct sound of 

musical instruments

Harmonics

5.6 Making simple calculations

Speed=​time​​distance​​

v=​t​​d​​

• v: speed (m/s)
  
• d: distance (m)
  
• t: time (s)
  

5.6 Making simple calculations

a) Two sound engineers wants to measure the speed of sound. They stand

594 meter apart. One send out a loud sound pulse using an electronic speaker. The other one measures how long it takes before he hears the sound. On average it took 1,8 seconds. Calculate the speed of sound.

b) The speed of sound in water is 1500 m/s. Calculate how long it would take to hear the pulse underwater.

5.6 Making simple calculations

• v: speed (m/s)
  
• f: frequency (Hz)
  
• λ: Wavelength (m)
  

v=f⋅λ

f=​T​​1​​

• f: frequency (Hz)
  
• T: Period (s)

Practice exercise

A sound wave with a frequency of 500 Hz Is traveling through a solid bar. The wavelength of this wave is 9.08 m. Which material is this sound wave traveling through?

A) Speed of sound in copper: 4600 m/s

B) speed of sound in gold: 3240 m/s

C) Speed of sound in glass: 4540 m/s

Traveling faster than sound

Mach 1, Mach 2, Mach 3

• Mach 1: traveling at 343 meters per seconds
  
• Mach 2: traveling at 686 meters per seconds
  
• Mach 3: 1029 meters per seconds
  
• The fastest skydiverer, Felix Baumgartner, traveled at mach 1.1, how fast did he fall?
  

5.7 Echoes

Echo location

Calculation exercise

A man has set out the find the deepest well in the world. Once he found it he clapped his hands above it. He timed how long it took before he heard an echo. It took 71.4 seconds. The speed of sound in air is 330 m/s. 

Calculate how deep the well is.

Calculation exercise

Dolphins can make sounds with a frequency as low as 0.2 Hz and as high as up to 150.000 Hz. A dolphin makes use of echo location. He sends out a signal, with fish floating 240 meters away.  It takes 0.32 seconds before he hear the echo. The wavelength of the sound wave he produced is 0.01875 m. Calculate the frequency of this sound wave.

Learning goals

• Explain how instruments get their distinct sound.
• Be able to do calculations on the speed of sound in different circumstances.
• Be able to calculate wave speed.
• Explain in your own words how echoes work.
• Describe how echo location works.
• Be able to do calculations involving echoes and echo location
• Explain how the mach system works.