Hearing Sound

1
Hearing Sound
2
Have you ever felt sound?
3
Have you ever felt sound?

• Car with really loud music playing (especially
  with heavy base).

4
Did you know?

• Thunder and lightening are essentially the same
  event?

5
Did you know?

• Thunder and lightening are essentially the same
  event?
• How can this be?????

6
Did you know?

• Thunder and lightening are essentially the same
  event?
• How can this be?????
• Light travels at 299,792 m/sec.
• Sound travels at 335 m/sec.

7
Can humans or animals hear better?
8
Can humans or animals hear better?

• Remember that sound is a vibration.

9
Can humans or animals hear better?

• Remember that sound is a vibration.
• Well.the frequency of a sound wave is the number
  of vibrations (waves) per second.

10
Can humans or animals hear better?

• Remember that sound is a vibration.
• Well.the frequency of a sound wave is the number
  of vibrations (waves) per second.
• We measure this in something called a Hertz (Hz).

11
Can humans or animals hear better?

• Remember that sound is a vibration.
• Well.the frequency of a sound wave is the number
  of vibrations (waves) per second.
• We measure this in something called a Hertz (Hz).
• 1Hz 1 wave per second

12
Can humans or animals hear better?
13
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.

14
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.
• Dogs can hear up to about 25,000 Hz.

15
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.
• Dogs can hear up to about 25,000 Hz.
• Cats can hear up to about 65,000 Hz.

16
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.
• Dogs can hear up to about 25,000 Hz.
• Cats can hear up to about 65,000 Hz.
• gt20,000 Hz ultrasonic.

17
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.
• Dogs can hear up to about 25,000 Hz.
• Cats can hear up to about 65,000 Hz.
• gt20,000 Hz ultrasonic.
• lt20 Hz infrasonic.

18
Can humans or animals hear better?

• Humans hear from about 20 to 20,000 Hz.
• Dogs can hear up to about 25,000 Hz.
• Cats can hear up to about 65,000 Hz.
• gt20,000 Hz ultrasonic.
• lt20 Hz infrasonic.
• Elephants communicate at this level.

19
Some common noises
20
Some common noises

• 20 (dB) whispers

21
Some common noises

• 20 (dB) whispers
• 40-50 (dB) Average home

22
Some common noises

• 20 (dB) whispers
• 40-50 (dB) Average home
• 70 (dB) City street

23
Some common noises

• 20 (dB) whispers
• 40-50 (dB) Average home
• 70 (dB) City street
• 115 (dB) rock concert

24
Some common noises

• 20 (dB) whispers
• 40-50 (dB) Average home
• 70 (dB) City street
• 115 (dB) rock concert
• 140-170 (dB) jet engine

25
Some common noises

• 20 (dB) whispers
• 40-50 (dB) Average home
• 70 (dB) City street
• 115 (dB) rock concert
• 140-170 (dB) jet engine
• 85 (dB) or higher for extended periods of time
  can cause permanent hearing loss

26
Ear Canal
27
The human ear Parts of the ear
28
The human ear Parts of the ear

• Outer ear funnels sound waves.

29
The human ear Parts of the ear

• Outer ear funnels sound waves.
• Ear canal a few cm long and ends at the eardrum.

30
The human ear Parts of the ear

• Outer ear funnels sound waves.
• Ear canal a few cm long and ends at the eardrum.
• Eardrum A small, tightly stretched, drum-like
  membrane that vibrates when hit by sound waves.

31
The human ear Parts of the ear

• Middle ear Contains the three smallest bones in
  the human body.

32
The human ear Parts of the ear

• Middle ear Contains the three smallest bones in
  the human body.
• Hammer Attached to the eardrum and vibrates and
  hits the anvil.

33
The human ear Parts of the ear

• Middle ear Contains the three smallest bones in
  the human body.
• Hammer Attached to the eardrum and vibrates and
  hits the anvil.
• Anvil shakes the stirrup.

34
The human ear Parts of the ear

• Middle ear Contains the three smallest bones in
  the human body.
• Hammer Attached to the eardrum and vibrates and
  hits the anvil.
• Anvil shakes the stirrup.
• Stirrup vibrates against the membrane separating
  the middle and inner ear.

35
The human ear Parts of the ear

• Inner ear Separated from middle ear by a
  membrane.

36
The human ear Parts of the ear

• Inner ear Separated from middle ear by a
  membrane.
• Cochlea cavity of the inner ear filled with
  liquid and Lined with thousands of tiny hairs.

37
The human ear Parts of the ear

• Inner ear Separated from middle ear by a
  membrane.
• Cochlea cavity of the inner ear filled with
  liquid and Lined with thousands of tiny hairs.
• The vibrations are passed from stirrup to
  membrane to liquid to hairs (which sway back and
  forth).

38
The human ear Parts of the ear

• Inner ear Separated from middle ear by a
  membrane.
• Cochlea cavity of the inner ear filled with
  liquid and Lined with thousands of tiny hairs.
• The vibrations are passed from stirrup to
  membrane to liquid to hairs (which sway back and
  forth).
• The hairs are attached to nerve cells that detect
  movement and send messages to the brain.

39
Applications of Sound

• Sonar (Sound navigation and ranging).
• Measuring the time it takes to detect a reflected
  sound wave.

40
Applications of Sound

• Ultrasound and infrasound
• Dog whistles (ultrasonic)
• Elephants stomping on the ground (produce sound
  waves too low for humans to hear). (infrasonic)

41
Applications of Sound

• Ultrasound (Echolocation)
• Using sound waves to determine distances or
  locate objects.
• Dolphins
• Bats

42
Applications of Sound

• Ultrasound (other uses)
• Medicine
• Brushing your teeth
• Jewelry cleaners
• Some cameras (automatic focus)