1. Frequency determines pitch
2.2
Frequency determines pitch

2. When you listen to music you hear both low and high sounds, right?

3. Frequency/Pitch Pitch- how high or how low sounds are
For most practical purposes the pitch is just the frequency
The frequency of a sound wave determines the pitch of the sound

4. Frequency
REMEMBER:
Frequency- the number of waves passing a fixed point in a given period of time

6. Frequency determines pitch
A high frequency wave, has short wavelengths.This makes a high pitched sound.
Ex: a piccolo

8. Question
If a high pitched sound has a high frequency and short wavelength would you say that the object is vibrating very fast or very slow?

9. Answer
A high pitched sound is produced by fast vibrations

10. Frequency determines pitch
A low frequency wave, which has a long wavelength, will make a low pitched sound.
Ex: a tuba, baritone sax

12. Question
What would you say about the speed of the vibrations from a low pitched sound?

13. Answer
The object that is producing a low pitched sound would vibrate slower than an object that produces a high pitched sound

14. HOW IS FREQUENCY RELATED TO PITCH?
High frequency = high pitch
Low frequency = low pitch

16. HIGH AND LOW FREQUENCIES
Remember:
Frequency is a measure of how often a wave passes a fixed point. One complete wave can be called a cycle.

17. HIGH AND LOW FREQUENCIES
Remember the unit for measuring frequency, and also pitch, is the hertz (Hz).
A hertz is one complete wave, or cycle, per second.

20. Question
If a wave has a frequency of 30, how many cycles would it have?

21. Answer 30 cycles or complete waves
This means that 30 complete waves will pass a given point in 1 second

22. Try this
Draw a 4Hz sound wave (label one wavelength and the resting line time as 1 second)

23. Try this
Draw a 12 Hz sound wave (label one wavelength and the resting ling time as 1 second)

24. Question
Compare the two waves. Does the 4Hz wave or the 12 Hz wave have a higher frequency? Which wave has a higher pitch? How can you tell?

25. Answer The 12 Hz wave has a higher frequency and a higher pitch.
We know this because frequency is defined as the amount of waves that pass a certain point in a certain time.
12 waves passing/second vs. 4 waves passing/second
Frequency relates to pitch so the 12 Hz wave also has a higher pitch

26. HUMAN EARS CAN HEAR A WIDE RANGE OF HEARING
Most people with good hearing can hear sounds in the range of 20Hz-20,000 Hz
The note middle C on a piano has a frequency of 262 Hz

28. HUMAN EARS CAN HEAR A WIDE RANGE OF HEARING
Infrasound-sounds that are below 20Hz
People cannot hear these sounds
Infrasound waves have a very LONG wavelength and can travel great distances without losing much energy.

30. HUMAN EARS CAN HEAR A WIDE RANGE OF HEARING
Ultrasound-waves in the range above 20,000 Hz
We cannot hear waves in the ultrasound range but many animals can and we also use ultrasound in many ways which we will learn later on.
A dolphin's sonar process, also used by bats and some whales, is called echolocation. Many of the clicks are at frequencies too high for the human ear to detect.
Sonar sends out sounds and waits for the sounds to bounce off other objects and come back (the same way an echo bounces back to us in a cave)

33. NATURAL FREQUENCIES
Tuning forks can be used by a piano tuner to match the piano string to the pitch made by a certain tuning fork.
Tuning forks of different sizes can be used to tune instruments to different pitches.

34. NATURAL FREQUENCIES
Resonance- the strengthening of a sound wave when a sound wave with a particular frequency encounters an object that has the same natural frequency
Constructive interference takes place and the amplitude of the initial sound wave is added with the sound from the vibrating object
When a tuning fork is struck, a nearby tuning fork with the same natural frequency will also begin to vibrate because of resonance.

35. SOUND QUALITY
Oscilloscope- a scientific instrument that tracks an electrical signal-The energy of a sound wave is converted into a signal and displays on an oscilloscope screen

36. THE MOTION OF THE SOURCE OF SOUND AFFECTS ITS PITCH
Doppler effect- the change in perceived pitch that occurs when the source or the receiver of a sound is moving

38. Doppler effect
In the 1800’s An Austrian scientist name Christian Doppler studied sound and made a hypothesis about sound waves.
His hypothesis was that pitch changes when a sound source moves rapidly toward and then away from a listener. It is the scientific principle we notice when sirens speed by us on the road.
In 1845 a Dutch scientist tested Doppler’s hypothesis and it was found to be correct.

39. FREQUENCY AND PITCH
The siren on the ambulance continually sends out sound waves. As the ambulance pulls closer to you, it catches up with the sound waves it is sending out. As a result, the sound waves that reach your ears are spaced closer together. The frequency, and therefore the pitch, is higher when it reaches you.
As the ambulance continues, it gets farther and farther away from you, while the sound waves still move toward you. Now the waves arrive farther apart. As the frequency decreases, you hear a lower pitch.