1
00:00:00,000 --> 00:00:02,000
We're known as the Treehouse Detectives.

2
00:00:02,000 --> 00:00:05,000
We're trying to get some sleep, but the neighborhood dogs are keeping us up.

3
00:00:05,000 --> 00:00:07,000
We want to know how our ears work.

4
00:00:07,000 --> 00:00:10,000
That way we can figure out why the dogs keep barking.

5
00:00:10,000 --> 00:00:11,000
And how sound travels.

6
00:00:11,000 --> 00:00:14,000
If we know how sound travels, that might help us solve the problem.

7
00:00:14,000 --> 00:00:17,000
I think I can help you out. Let's move into the other room.

8
00:00:18,000 --> 00:00:20,000
What is all this stuff?

9
00:00:20,000 --> 00:00:22,000
This is equipment we use to test people's hearing.

10
00:00:22,000 --> 00:00:24,000
Could you tell us how our ears work?

11
00:00:24,000 --> 00:00:27,000
Sure. The outer ear collects and concentrates the sound energy.

12
00:00:27,000 --> 00:00:33,000
Then this is channeled down the ear canal, and the eardrum vibrates, and so do the small bones within the ear.

13
00:00:33,000 --> 00:00:36,000
Then the sounds go through the cochlea, the hair cells bend,

14
00:00:36,000 --> 00:00:41,000
and then the impulses are sent up the auditory nerve into the brain, where they're decoded.

15
00:00:41,000 --> 00:00:43,000
Other sounds people can't hear?

16
00:00:43,000 --> 00:00:45,000
Sure, if they're above a certain frequency.

17
00:00:45,000 --> 00:00:50,000
The human ear can hear frequencies between 20 and 20,000 vibrations a second.

18
00:00:50,000 --> 00:00:53,000
Frequencies. Hmm. That might be a clue.

19
00:00:53,000 --> 00:00:54,000
Thanks for all your help.

20
00:00:54,000 --> 00:00:55,000
Sure. Bye.

21
00:00:55,000 --> 00:00:56,000
Bye, and good luck!