definitions - 32

Question 1

This factor is the percentage of normal observers who may be expected to experience visual comfort in a particular environment with a particular lighting situation.

Answer 1

visual comfort probability VCP

Question 2

are a complex interaction of light source and brightness, position of the task, reflectivity of the task, and position of the eye.

Answer 2

veiling reflection

Question 3

a measure of speech intelligibility calculated from the number of words read from a selected list that are understood by an audience.

Answer 3

articulation index

Question 4

the reduction of sound

Answer 4

attenuation

Question 5

a single-number rating of a floor-ceiling’s impact sound transmission performance at various frequencies

Answer 5

impact isolation class IIC

Question 6

a set of single-number ratings of acceptable background noise corresponding to a set of curves specifying sound pressure levels across octave bands.

Answer 6

noise criteria NC

Question 7

a single-number rating of noise reduction

Answer 7

noise isolation class NIC

Question 8

the arithmetic difference, in decibels, between the intensity levels in two rooms separated by a barrier of a given transmission loss.

Answer 8

noise reduction NR

Question 9

:the persistence of a sound in a room after the source has stopped producing the sound

Answer 9

reverberation

Question 10

the time it takes the sound level to decrease 60 dB after the source has stopped producing the sound

Answer 10

reverberation time

Question 11

the unit of absorption; theoretically, 1 ft of surface having an absorption coefficient of 1.00

Answer 11

sabin

Question 12

a single-number average over several frequency bands of a barrier’s ability to reduce sound.

Answer 12

sound transmission class STC

Question 13

the difference, in decibels, between the sound power incident on a barrier in a source room and the sound power radiated into a receiving room on the opposite side of the barrier. The transmission loss varies with the frequency being tested.

Answer 13

Transmission loss (TL)

Question 14

Sound has three basic qualities:

Answer 14

velocity frequency and power

Question 15

inverse square law

Answer 15

The basic inverse square law is where sound intensity is inversely proportional to the square of the distance from the source.

Question 16

is the bending of sound waves around an object or through an opening. Diffraction explains why sounds can be heard around comers and why even small holes in partitions allow so much sound to be heard.

Answer 16

diffraction

Question 17

is the random distribution of sound from a surface. It occurs when the surface dimension equals the wave- length of the sound striking it.

Answer 17

diffusion

Question 18

The drain that removes dirt that builds up in the floor pool of an evaporative cooling tower.

Answer 18

blow down

Question 19

In sanitary drainage, any vent that serves two or more traps.

Answer 19

circuit vent

Question 20

The ratio of useful light arriving at the work plane to the amount of light emitted by the source.

Answer 20

coefficient of utilization

Question 21

The ratio of the amount of heat energy delivered by a heat pump to the amount of energy supplied, or the ratio of the amount of heat energy removed by a refrigeration machine to the amount of energy expended in its removal. It is similar to efficiency, but often exceeds 100 percent, and is therefore expressed as a number, i.e., 2.7, which is typical for a heat pump.

Answer 21

coefficient of performance

Question 22

A decibel measured in the A scale, that is weighted to account for the special sensitivi- ties of the human ear.

Answer 22

dbA

Question 23

A method of connecting windings on a three phase transformer, end to end, that results in a triangular shape.

Answer 23

delta connection

Question 24

A device through which the air from a duct enters a room, or a device through which the light from a fixture enters a room.

Answer 24

diffuser

Question 25

A unit of liquid flow used in sizing both supply and drainage pipes.

Answer 25

fixture unit

Question 26

A valve that releases a definite amount of water into a plumbing fix- ture each time it is actuated.

Answer 26

flushometer valve

Question 27

The basic unit of illumination arriving at a work plane. Is equal to one lumen per square foot.

Answer 27

footcandle

Question 28

A thermometer that measures Mean Radiant Temperature (MRT).

Answer 28

globe thermometer

Question 29

A refrigeration loop used to bring heat into a space instead of removing heat from it. The term is also used for an entire system of such units attached to a recirculating heat sink.

Answer 29

heat pump

Question 30

The intensity of sound at a given location, measured in watts per square meter, or more commonly in dB where the reference level is 10- 12 watts/meter 2 or 10- 16 watts/ cm 2 .

Answer 30

intesity level IL

Question 31

A physical principle that states that the intensity of a phenomenon is inversely proportional to the square of the distance from the source to the measuring device. It holds true for point sources of light, and for sound in an open field.

Answer 31

inverse square law

Question 32

A process of water soften- ing in which calcium and magnesium ions are replaced by sodium ions. This process is also known as the zeolite process.

Answer 32

ion exchange

Question 33

A unit of light, defined as the amount of light passing through one square foot at a distance of one foot from a one candlepower source.

Answer 33

lumen

Question 34

The theoretical law that states that for each doubling of mass in a wall, there is a 6 dB drop in the amount of sound transmitted.In actual practice, it is usually closer to 5 dB.

Answer 34

mass law

Question 35

The weighted average of all of the temperatures of all of the surfaces visible from a given position.

Answer 35

mean radiant temperature MRT

Question 36

A one- number rating system giving the average sound absorption coefficient of a material at frequen- cies of 250, 500, 1,000 and 2,000 Hz.

Answer 36

noise reduction coefficient NRC

Question 37

A single-number system for specifying a maximum SPL level in a given location, using standardized reference contours. The curves weight the frequencies to which the human ear is sensitive.

Answer 37

NC curves

Question 38

A subjective system of measuring loud- ness, based on the reference point of one equal to a sound pressure level of 40 dB.

Answer 38

sone

Question 39

The loga- rithmic expression of the pressure exerted by sound waves on the receiver.

Answer 39

sound pressure level SPL

Question 40

A method of connecting the windings on a three-phase transformer in which one end of all three windings is connected to a common neutral center point, forming a Y shape. Same as Wye Connection.`

Answer 40

star connection

Question 41

The method of using a heated surface and the resulting convection to move a fluid out of a space. In solar hot water heaters, the collector is below the storage tank, and the water is circulated automatically by convection when it is heated.

Answer 41

thermosiphon

Question 42

The reduction of sound that occurs when a given wall transmits sound from one room to an adjacent room, expressed in decibels.

Answer 42

transmission loss TL

Question 43

A substance used in water softening, in which a filtering tank is recharged by passing a salt solution through it. The tank may then be used as a filter for the free ions associated with hard water.

Answer 43

zeolite

Question 44

An automatic valve that admits air into a supply pipe rather than allow- ing the pipe to suction or siphon polluted water back into the supply.

Answer 44

vacuum breaker