1. Sound

2. Outcomes
1. Describe the sonic spectrum and the range of human hearing.
2. Describe the motion of air molecules as sound waves travel past them.
3. Relate the pitch of sound to frequency.
4. Describe the characteristics of a sound wave that determine loudness and quality.
5. Compare the transmission of sound through air, solids, liquids, and a vacuum.
6. Describe factors that affect the speed of sound.
7. Give examples of forced vibrations.
8. Describe the conditions necessary for resonance to occur.
9. Describe the conditions necessary for beats to occur.
10. Describe the decibel scale of relative intensities.
11. Match structures of the human ear with their function.

3. Characteristics of Sound Lab
Demo with keyboard
Program

4. If a tree falls in the woods and there is no one there to hear it, does it make a sound?

5. The Origin of Sound
All sounds are produced by the vibrations of material objects.
Vibrating material sends a disturbance through a medium (usually air) in the form of a longitudinal wave.
Under normal conditions, the frequency of the source = the frequency of the waves produced.
Pitch—our subjective impression of the frequency of a sound.
People with normal hearing can perceive pitches with frequencies from 20 Hz to 20,000 Hz.
Infrasonic—sound waves with frequencies below 20 Hz.
Ultrasonic—sound waves with frequencies above 20,000 Hz.

6. Sound in Air and Media that Transmit Sound
Compression—a pulse of compressed air.
Rarefaction—a region (pulse) of low pressure air.
Remember: It is the pulse that travels; not the medium.
In general, sound is transmitted faster in liquids than gases, and still faster in solids.
Sound cannot travel in a vacuum.

7. The Sonic Spectrum – all mechanical, longitudinal waves.

8. Boy bands

9. Sound Ranges Infrasonic – less than 20 Hz
Ultrasonic – more than 20,000 Hz
Range of Human Hearing
20 – 20,000 Hz
0 – 120 dB

11. Typical Loudspeaker Driver Ranges
Driver Type
Minimum Frequency
Maximum Frequency
Subwoofer
< 20Hz
100Hz
Woofer
40Hz
300-3kHz
Mid Woofer
3kHz
Midrange
300Hz
Tweeter
1.5kHz
> 20kHz
Super Tweeter
10kHz
30kHz

12. Approximate Range (Hz)
Species
Approximate Range (Hz) 
human
64-23,000
dog
67-45,000 
cat
45-64,000 
cow
23-35,000 
horse
55-33,500 
sheep
100-30,000 
rabbit
360-42,000 
rat
200-76,000 
mouse
1,000-91,000 
opossum
500-64,000 
guinea pig
54-50,000 
hedgehog
250-45,000 
raccoon
100-40,000
ferret
16-44,000 
chinchilla
90-22,800 
bat
2, ,000 
beluga whale
1, ,000
elephant
16-12,000 
porpoise
75-150,000
goldfish
20-3,000 
catfish 
50-4,000 
tuna 
50-1,100 
bullfrog 
100-3,000 
tree frog
canary 
250-8,000 
parakeet 
200-8,500 
cockatiel
owl 
200-12,000 
chicken 
125-2,000 

13. What do these sound like?
We hear from Hz.
Will 2000 Hz sound “high”, “medium” or “low” pitched?
Predict

14. Speed of Sound Distance and time Wavelength and frequency
Characteristics of the material the sound is traveling in

15. Speed of Sound In air, sound travels about 330 meters per second.
Water vapor in the air increases this speed slightly.
Increased temperature also increases this speed.
Each degree increase above 0o C increases the speed of sound by 0.60 m/s.
Sound travels 4 times faster in water than in air and 15 times faster in steel than in air.
Sound travels faster through elastic materials than inelastic materials.
Elasticity—the ability of a material to change shape in response to a force and then regain its initial shape.
Example: Steel
Example of an inelastic material: putty

16. Speed of Sound in Air Sound Travels Faster in Hotter Air

17. At 25°C

18. At -25°C

19. Ear Diagram
Test questions require that you match important structures with their function.
You will not have to label or identify structures on a diagram.

20. What are the functions of…
Outer ear
Middle ear
Inner ear

21. What do these do? middle ear bones- amplify the sound
cochlear hair cells- stimulate nerve cells when moved
auricle/pinna- collects sound from outside
auditory nerve
tympanic membrane- can be scarred by loud sounds
auditory canal
Cochlea- transmits sound through a fluid
round window

22. Auditory nerve 8

23. Size of the ossicles

24. Size of the cochlea

25. “tubes”