Frequency Determines Pitch

1
Frequency Determines Pitch

• Sect. 16-2

2
3 Min. Warm-up

• Decide if these statements are true. If not
  true, correct them.
• In a longitudinal wave, the vibrations move
  perpendicular to the direction of the wave.
• Sound is a type of electromagnetic wave.
• Vibrations pass through many parts of the ear,
  not just the eardrum.

3
3 Min. Warm-up

• Decide if these statements are true. If not
  true, correct them.
• In a longitudinal wave, the vibrations move in
  the same direction as the wave.
• Sound is a type of mechanical wave
• Vibrations pass through many parts of the ear,
  not just the eardrum. True

4
Pitch

• The quality of the highness or lowness of a
  sound.
• Determined by frequency
• Very fast vibrating object produces high sound
• Slow vibrating objects produces a low sound
• High frequency makes high sound
• Low frequency makes low sound

5
Explore Pitch

• Why does the sound change?pg. 525
• What happened to the sound as you slid the ruler
  back?
• Describe the motion of the ruler.

6
Explore Pitch

• Why does the sound change?pg. 525
• What happened to the sound as you slid the ruler
  back? The sound became higher
• Describe the motion of the ruler. The ruler
  moved up and down a greater distance when the
  ruler extended farther than when it was pulled
  back on the desk

7
Vocabulary

• Hertz unit for measuring frequency and pitch
  one complete wave per second
• Ultrasound sound waves in the range above
  20,000 hertz
• Resonance strengthening of a sound wave when it
  combines with an objects natural vibration.
• Doppler Effect the change in observed pitch
  that occurs when the source or the one who hears
  a sound is moving.

8
Sound is a type of mechanical wave.

• Why?
• It transfers energy through a medium.
• It is produced by a vibrating object and travels
  through matter
• The disturbances that travel in a sound wave are
  vibrations.

9
How is frequency related to pitch?

• The higher the frequency of the sound wave, the
  higher pitched the sound.

10
Which instrument makes the lower pitched sound?

• A flute
• A tuba

11
Which instrument makes the lower pitched sound?

• A tuba

12
High and Low Frequencies

• Frequency is a measure of how often a wave passes
  a fixed point in a certain amount of time.
• One complete wave is also called a cycle
• Hertz 1 cycle or wavelength/second
• A wave with a frequency of 4 hertz has 4 cycles
  per second

13
Frequency Range of Most People with Good Hearing

• 20 20,000 Hertz

14
Infrasound waves

• Sound waves with frequency below 20 Hertz. They
  have very long wavelengths and can travel great
  distances without losing much energy.

15
Ultrasound

• Sound waves above 20,000 hz
• Humans cannot hear it.
• Many animals can hear it.

16
Natural Frequencies

• You may see a piano tuner tap a tuning fork
  against another object. The tuner does this to
  make the fork resonate at its natural frequency.
  He tunes the piano strings to match it.

17
Resonance

• Causes sound waves to strengthen
• Results from adding the amplitude of a sound wave
  to the amplitude of an objects natural vibration

18
Resonance cont.

• When a tuning fork is struck, a nearby tuning
  fork with the same natural frequency will also
  vibrate because of resonance.

19
Sound Quality

• A. Timbre
• 1. Most sounds are a combination of waves.
• 2. The combination of pitches is the main factor
  affecting the quality of sound
• Pitch that you hear is called fundamental pitch
• Higher-frequency pitches are called overtones
• This is why two singers can sound very different
  when singing the same note.

20
Sound Quality

• B. The way a sound starts and stops
• 1. The sound of cymbals blast out suddenly
• 2. The sound of the human voice starts much more
  gently.

21
What two factors affect sound quality?
22
What two factors affect sound quality?

• Overtones - Combination of pitches
• The way the sound starts and stops

23
The motion of the source of a sound affects its
pitch.

• If an ambulance passed you, would you hear the
  same sound the whole time? Why or Why not?

24
The motion of the source of a sound affects its
pitch.

• No, the ambulance blasts the same pitches the
  whole time, but the pitch falls as the ambulance
  drives away.

25
Doppler Effect

• The change in perceived pitch that occurs when
  the source or the receiver of a sound is moving.

26
How does the motion of a sound source affect its
pitch?

• If a sound moves toward the listener, the pitch
  rises. If it moves away from the listener, the
  pitch lowers.