Kaplan- Lesson 8: Acoustics

Question 1

Just as we perceive the wavelength of light in color, we perceive the wavelength of sound in terms of its _____.

Answer 1

pitch

Question 2

One complete wave form is called a _____.

Answer 2

cycle

Question 3

One cycle per second is more commonly known as _____.

Answer 3

Hertz

60cps = 60 Hertz

Question 4

The human ear is most sensitive to sounds in what range?

Answer 4

125 - 6,000 hertz

Question 5

The basic unit of sound intensity level is called the _____.

Answer 5

decibel

Question 6

The human ear is more sensitive to sounds in the middle frequencies. The scale that most closely represents the response of the human ear is called _____.

Answer 6

The A scale.

units- dBA

Question 7

What is the unit for the acoustical measure of reflectivity and absorptivity?

Answer 7

Sabin (α)- after Wallace Clement Sabin

Question 8

What is reverberation?

Answer 8

The slow fading of a sound in an enclosed space.

Question 9

What is reverberation time?

Answer 9

The amount of time that elapses before there is complete silence after a 60 dB sound.

Question 10

What is sound transmission class (STC)?

Answer 10

A method of rating walls, doors, etc. in terms of their typical or overall resistance to sound transmission.

Question 11

How is impact isolation class determined?

Answer 11

By the use of a tapping machine and sound meter to measure the SPL at different frequencies.

Question 12

T/F The best location for a sound barrier wall is in the middle of the source and the receiver?

Answer 12

False. The best location is very close to the source or very close to the receiver.

Question 13

What criteria are used in specifying the maximum noise level in a given space under a given set of conditions?

A. PWL (sound power level)
B. NRC (noise reduction coefficient)
C. NC (noise criteria)
D. NR (noise reduction)

Answer 13

C. NC (noise criteria)

Question 14

What is the logarithmic measure of the intensity of a sound relative to a reference intensity in watts/m^2 or watts/cm^2?

A. IL (sound intensity level)
B. SPL (sound pressure level)
C. STC (sound transmission class)
D. NC (noise criteria)

Answer 14

A. IL (sound intensity level)

Question 15

Which of the following is a method of rating wall sections or doors according to their typical or overall resistance to sound transmission?

A. SPL (sound pressure level)
B. STC (sound transmission class)
C. PWL (sound power level)
D. NR (noise reduction)

Answer 15

B. STC (sound transmission class)

Question 16

Reverberation time is

I. the time required for a sound to decay 60 dB in a space.

II. the time it takes for an echo to return.

III. longer in a dead space, and shorter in a live space.

A. I only
B. II & III
C. I & III
D. I, II, & III

Answer 16

A. I only

the time required for a sound to decay 60 dB in a space.

Question 17

The maximum acceptable IL for a hospital is

A. 100 dB
B. 70 dB
C. 40 dB
D. 10 dB

Answer 17

C. 40 dB

Question 18

Doubling the distance from the source to the receiver would result in a

A. drop of 6 dB.
B. gain of 6 dB.
C. drop of 3 dB.
D. gain of 3 dB.

Answer 18

A. drop of 6 dB.

Question 19

Doubling the number of sources at a given intensity would result in a

A. drop of 6 dB.
B. gain of 6 dB.
C. drop of 3 dB.
D. gain of 3 dB.

Answer 19

D. gain of 3 dB.

Question 20

Doubling the mass of a theoretical wall causes its sound transmission to

A. decrease 6 dB.
B. increase 6 dB.
C. decrease 3 dB.
D. increase 3 dB.

Answer 20

A. decrease 6 dB.

Question 21

Given a concrete room with concrete walls, floors, and ceiling, adding carpeting and drapes does which of the following?

I. Increases the absorptivity of the room.

II. Decreases the reverberation time of the room.

III. Decreases the intensity of the sound that a small motor would make in the room.

A. I only
B. II & III
C. I & III
D. I, II, & III

Answer 21

D. I, II, & III

Question 22

A partition with a sound transmission class rating of 55 dB would be

A. very good at stopping reflected sound.

B. barely acceptable at stopping transmitted sound.

C. very good at stopping transmitted sound.

D. barely acceptable at stopping reflected sound.

Answer 22

C. very good at stopping transmitted sound.