Physics Chapter 5, Section 4
Sounds from Vibrating Air
HW: p 526 #1, 4-6
 Learning Objective
 Explain how sound is produced by
longitudinal compression waves
 Write a conclusion that includes IV,
DV, evidence, and the big idea
 Success Criteria
 Identify standing waves in different
kinds of air-filled tubes
 Observe how pitch changes with the
length of the tube
 Observe the effect of closing one end
of the tube on the pitch of the sound
 Observe sound bending around
corners and spreading
 Relate observations of pitch to
drawings of standing waves
 Organize observations to find a pattern
 Do Now
 Write LO and SC on
new left page
 p 518 WDYS/WDYT
 Agenda
 Do Now
 Investigation 5.4
 Summary
Investigation 5.4
 Part A (groups)
 1-3 - with straws
 4, 5 with test tubes
 Part B
 1 - Class demo
 2 - with group
 Part C
 In groups
HW: p 526 #1, 4-6

Learning Objective
 Explain how sound is produced by
longitudinal compression waves
 Write a conclusion that includes IV, DV,
evidence, and the big idea

Success Criteria
 Identify standing waves in different kinds of
air-filled tubes
 Observe how pitch changes with the length
of the tube
 Observe the effect of closing one end of the
tube on the pitch of the sound
 Observe sound bending around corners and
spreading
 Relate observations of pitch to drawings of
standing waves
 Organize observations to find a pattern
 Do Now
 How did closing the
end of the tube
change the sound?
 Agenda
 Do Now
 Investigation 5.4
 Summary
Physics Talk 5.4
 What kind of waves
does sound make?
 Compressional
(longitudinal) waves
 How does this relate
to springs?
QuickTime™ and a
decompressor
are needed to see this picture.
Physics Talk 5.4
 What was the
medium the sound
traveled through?
 The air in the straw
or tube
Physics Talk 5.4
 How do these related
to the standing
waves created by the
stringed instrument?
 Air molecules cannot
vibrate at the bottom of
the test tube, so this is a
node of the wave
 The open end of the test
tube provides the wave’s
amplitude
 The vibration of the air at
this end, is the sound you
hear
 This is the antinode of the
wave
Physics Talk 5.4
 What is diffraction?
 The ability of sound
waves to spread out
or change direction
as the emerge from
an opening
 This is why you can
hear someone talking
around a corner
Physics Talk 5.4
 The top show a large
amount of diffraction,
when the opening is
smaller
 The bottom shows a
small amount of
diffraction, since the
opening is larger
Physics Talk 5.4
 How do megaphones
work?
 A megaphone
increases the
diffraction of sound,
due to the small
opening you tell into
 The best opening size
depends on the
sound being
produced
Vibrating Columns of Air
QuickTime™ and a
decompressor
are needed to see this picture.
Physics Talk
 How does changing
wavelength effect
frequency?
 When keeping a
constant wave speed,
increasing the
wavelength will
decrease the
frequency - causing a
lower pitch
Physics Talk 5.4
 Open tube
wavelength
 Closed tube
wavelength
 Half of the
wavelength will fit
 The wavelength is 2x
the length of the
tube
 One quarter of the
wavelength will fit
 The wavelength is 4x
the length of the
tube
Physics Talk 5.4
 Why does the closed
straw have a lower
pitch?
 Why does the open
straw have a higher
pitch?
 The wavelength is
longer (4x), meaning
the frequency is
lower
 The wavelength is
shorter (2x),
meaning the
frequency is higher
What do you think now?
 How do flutes and organ pipes produce
sound?
USE PHYSICS!