Module 8 : Sounds in the Wild

Question 1

Sound does not travel forever. over a distance, sound losses amplitude. As the sound pressure wave travels out from the source, what happens ?

Answer 1

The pressure of sound is dispersed over a greater area the further it is from the sound source.

Question 2

As the distance from a sound source increases, what also happens?

a) The amplitude increases by 6 DB
b) the frequency increases
c) the Threshold decreases to 55 dB SPL
d) The intensity decreases

Answer 2

d) The intensity decreases

Question 3

So the intensity decrease at a rate equal to?

Answer 3

1/r^2

r=is a relative distance to the source

Question 4

The loss of sound pressure results in a ___ dB loss in the amplitude of the sound for every doubling of the distance.

Answer 4

6dB

Look at figure “sound over distance “

Question 5

Anything that changes a sound is said to ____with the sound.

Answer 5

Interference

Question 6

If the amplitude of the sound decreases during interference , the amplitude of the sound is said be to be?

Answer 6

destructive interference

Question 7

If the sound levels of the sound increase during interference, this is said to be called?

Answer 7

Constructive interference

Question 8

As sound spreads out from the source, it often encounters other sounds in the environment. Sound pressure adds together perpendicularly. True or false.

Answer 8

False. Sound pressure adds linearly

Question 9

When sound spreads outs and encounters other sounds, it add together. If both sounds have positive or negative pressure, the amplitude ____.

Answer 9

increases.

Question 10

When sound spreads outs and encounters other sounds, it add together. If one sound is in compression and the other in rarefaction, the amplitude of the sound____.

Answer 10

decreases

Question 11

Anytime a sound encounters an object the same size or larger than the sounds wavelength, what is created?

Answer 11

A sound shadow.

Question 12

True or false: The shadow or null area behind the object, will extend at least the wavelength of the sound?

Answer 12

True

Question 13

What is the reflection of sound in an environment that then blends with the perception of the original sound?

Answer 13

Reverberation

Question 14

We measure reverberation by measuring:

a) the length of time is takes to cut the frequency time in half
b) The amplitude length of the sound during compression and rarefaction
c) The time it takes for a sound to decrease by 60 dB after the sound has stopped.
d) The time it takes for a sound to increase by 60 dB after the sound has stopped

Answer 14

c) The time it takes for a sound to decrease by 60 dB after the sound has stopped.

Question 15

The greater the reverberation time, the _____ the environment.

Answer 15

Noiser

Question 16

Environments with hard surfaces in them are ____ than environments with lots of soft materials

Answer 16

more reverberant

Question 17

True or false: Our auditory system cannot seperate out the direct sound from the reverberated sound because it happens so quickly.

Answer 17

True

Question 18

What is the name of a room that prevents all reverberation?

Answer 18

Anechoic Room

Question 19

What is the sound reflecting back from a greater distance so it does not mingle in auditory perception with the original sound?

Answer 19

An echo

Question 20

When an ongoing sound bounces off a wall and back into the room, it can bounce BACK OVER ITSELF.If the frequency of the sound and the width of the room are related just right, what is formed?

Answer 20

A STANDING WAVE

Question 21

Original wave + reflected wave=?

Answer 21

standing wave.

Question 22

The areas of the standing wave that oscillates between compression and rarefaction is the _____ of the standing wave.

Answer 22

antinode

Question 23

Antinodes have a weaker amplitude than the original sound . T/F

Answer 23

False. Antinodes have a greater amplitude than the original sound

Question 24

What is the area of the standing wave that appear to stand still and have no change in pressure, called?

Answer 24

NODES

Question 25

WHY can’t you hear the sound of nodes?

Answer 25

because the rarefaction and compression of the original wave are canceled out by the rarefaction and compression of the reflected wave.

Question 26

In a room with a standing wave, you can hear the sound in one spot, then move to one side or the other and the sound can no longer be heard. If you heard the standing wave, you are standing in a(n) ____. If you can’t hear the standing wave, you are standing in a(n) _____.

Answer 26

antinode

node

Question 27

The wavelength of the lowest frequency that can form a standing wave in the room, is the frequency with ?

Answer 27

twice the width of the room.

Formula for fundamental frequency for standing wave in a room is:

f0= C/2L

Fundamental frequency=speed of sound divided by two times the length of the room.

Question 28

If you move closer to the source of a sound by half distance, how much does the dB level increase?

a) 3 db
b) it doubles
c) 6 db
d) 12 db

Answer 28

c) 6 db

Question 29

Which of the following results from destructive interference?

a) increase in the frequency of sound
b) reduction in the frequency of a sound
C) increase in sound amplitude
d) reduction in sound amplitude

Answer 29

-reduction in sound amplitude

Question 30

Which of the following describes an antinode in a standing wave?

a) a point of minimum amplitude
b) the point of sound reflection
c) a point of maximum amplitude

Answer 30

C

a point of maximum amplitude

Question 31

Reverberation and an echo are the exact sam thing.

True or false.

Answer 31

FALSE