Ch 20 Acoustics

Question 1

Sound has three basic qualities:

Answer 1

velocity, frequency, power

Question 2

this depends on the medium in which the sound is travelling and the temperature of the medium

Answer 2

velocity

Question 3

the number of cycles completed per second and is measured in hertz

Answer 3

frequency

Question 4

the quality of acoustic energy as measured in watts

Answer 4

power

Question 5

By definition, ___ dB is the threshold of human hearing, and ___ dB is the threshold of pain.

Answer 5

0 —– 130

Question 7

A healthy young person can hear sounds in the range of about __ to __.

Answer 7

20Hz — 20000Hz

Question 8

There are two basic problems in controlling noise:

Answer 8

preventing the transmission of sound from one space to another and reducing the noise within a space

Question 10

takes into the account only the loss through the partition

Answer 10

transmission loss

Question 11

dependent on the area of the partition separating the two spaces and the absorption of the surfaces in the quiet room

Answer 11

noise reduction

Question 12

a single number rating used to the transmission loss of construction

Answer 12

sound transmission class (STC)

Question 13

The ___ the STC rating, the better the barrier is in stopping sound

Answer 13

higher

Question 14

A material with a coefficient below __ is considered to be reflective and one with a coefficient above __ is considered sound absorbing.

Answer 14

0.2 —- 0.2

Question 15

used to control unwanted sound reflection improves speech privacy and decrease or increase reverberation

Answer 15

sound absorption

Question 16

the ratio of the sound intensity absorbed by the material to the total intensity reaching the material. ranges from 0 - 1.

Answer 16

coefficient of absorption

Question 17

Although absorptive materials can be placed anywhere, ___ for sound absorption is more effective in large rooms, while ____ is more effective in small rooms.

Answer 17

ceiling treatment —— wall treatment

Question 18

the average of a material’s absorption coefficients at the four frequencies of 250, 500, 1000, and 2000 Hz, rounded to the nearest multiple of 0.05

Answer 18

noise reduction coefficient (NRC)

Question 19

The recommended time for speech reverberation in offices and small rooms is __ to __ seconds, while for auditrium it is __ to __.

Answer 19

0. 3 - 0.6 seconds for small rooms

1. 5 - 1.8 for large spaces

Question 20

The average absorption coefficient of a room should be at least __. An absorption above __ is usually not desirable or economically justifiable.

Answer 20

0.20, 0.50

Question 21

These 3 methods can be used to build a sound-resistant partition:

Answer 21

add mass to the wall, add insulation between studs and resilient channels on one side of the partition

Question 22

the prologation of sound as it repeatedly bounces off hard surfaces

Answer 22

reverberation

Question 23

These are the 3 primary ways sound can be controlled within a space:

Answer 23

by reducing the level of loudness of the sound source, by modifying the absorption of the space and by introducing non-intrusive background noise

Question 24

There are 5 important factors in designing for speech privacy in an open area. All must be present to achieve the optimum acoustic environment

Answer 24

ceiling must be highly absorptive, area must include space dividers to reduce transmission, other surfaces should be designed to not reflect sound, if possible activities should be distanced to take advantage of normal attenuation of sound with distance and properly designed background masking systems

Question 25

sound resulting from direct contact of an object with a sound barrier can occur on any surface, but it generally occurs on a floor and ceiling assembly is called

Answer 25

impact noise

Question 27

These 6 ideas help minimize acoustic problems in interior space planning:

Answer 27

plan similar use areas next to each other, use buffer spaces such as closets, stagger doorways across the corridor, try to locate furniture so that areas producing noise are not close to the wall, minimize the area of the common wall and avoid room shapes that reflect or focus sound

Question 31

a piece of hardware that drops a seal from the door to the floor or threshold as the door closes

Answer 31

automatic door bottom

Question 37

a single number rating of a floor/ceiling’s impact sound performance

Answer 37

insulation class (IIC)

Question 38

the _ the IIC rating, the better the floor performs in reducing impact sounds in the test frequency range

Answer 38

higher

Question 45

a single number rating of the average sound absorption of a material over a limited frequency range including 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz rounded to the nearest multiple of 0.05

Answer 45

noise reduction coefficient (NRC)

Question 46

single number rating but the frequency range includes 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz.

Answer 46

speech range absorption (SRA)

Question 47

single number measure of the transmission loss through ceiling tiles between two closed rooms where there is no wall or other barrier above the suspended ceiling

Answer 47

ceiling attenuation class (CAC)

Question 48

a single number summation of how effective a ceiling is in absorbing sound reaching it form over low partitions

Answer 48

articulation class

Question 49

measures the performance of all the elements of a particular configuration working together. predicts the intelligibility of speech for a group of talkers and listeners

Answer 49

articulation index