Chapter 4 | Sound Waves

Question 1

The well-known St. Paul’s Cathedral’s whispering gallery, so called because a speaker standing against the gallery wall can whisper and be heard by someone standing against the wall on the opposite side of the room. Why does this work?

Answer 1

• Shape of room (circular) allows sound to travel

- Longitudinal waves can reflect

Question 2

Sound is?

Answer 2

Vibrations of pressure in a medium like air, which then causes the human eardrum to vibrate. (Brain perceives sound)

Question 3

Name some characteristics of sound.

Answer 3

-It’s a longitudinal wave, parallel movement
-It’s a Mechanical wave, must have a medium!
(Air/Water/Solid)

Question 4

What are compressions?

Answer 4

They’re the squashed together areas in longitudinal waves.

Question 5

What are rarefactions?

Answer 5

They’re the stretched-out areas of longitudinal waves.

Question 6

Why does sound travel slower through air but faster through liquid and solids?

Answer 6

More densely packed particles, like a solid transfer the energy more easily.

Question 7

What is the Decibel Scale?

Answer 7

It’s the measurement of sound loudness (intensity).

[Greater the amplitude (loudness) = greater the energy carried by the sound waves]

Question 8

What happens with every increase of 10 dB?

Answer 8

It gets 10x louder.

Example:
0 dB to 20 dB
10 x 10 = 100x louder

Question 9

From what decibel point to which point do we start to feel pain?

Answer 9

The lowest we can hear is 0 dB, the Threshold of hearing, the loudest we can hear (with irreparable damage) is 130 dB, the threshold of pain.