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ARE 5.0 PPD - Project Planning & Design > Light & Acoustics > Flashcards

Light & Acoustics Flashcards

1
Q

<p>Definition of light</p>

A

<p>visually evaluable radiant energy</p>

<p>visible spectrum on EM radiation</p>

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2
Q

<p>Coefficient of transmission</p>

A

<p>total light transmitted through a material</p>

<p>clear glass = 85% transmittance</p>

<p>translucent = transmits light, but not a clear image</p>

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3
Q

<p>Reflectance/reflectance coefficient</p>

A

<p>ratio of total reflected light to total incident light</p>

<p>reflection can be specular (mirror-like), diffuse (from uniformly rough surfaces), or combined (brighter and duller points)</p>

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4
Q

<p>Eye parts to process light</p>

A

<p>cones perceive detail and color, more near the fovea</p>

<p>rods perceive motion and light, surround the fovea</p>

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5
Q

<p>Candlepower</p>

A

<p>unit of luminous intensity that is equal to horizontal output of a wax candle</p>

<p>aka candela</p>

<p>radiant energy output</p>

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6
Q

<p>Illuminance</p>

A

<p>density of luminous flux incident on a surface (lumens per unit area)</p>

<p>one lumen uniformly incident on 1 sq ft = 1 foot-candle (fc)</p>

<p>radiant energy shining on a surface</p>

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7
Q

<p>Lumen</p>

A

<p>(lm) = the unit of luminous flux equal to a unit solid angle of 1 steradian (square radian, like a 3D ray)Âfrom a uniform point source of 1 candlepower</p>

<p>radiant energy in a given 3D shape</p>

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8
Q

<p>Luminance</p>

A

<p>the luminous flux per unit of projected/apparent area and unit solid angle leaving a surface, either reflected or transmitted, unit of candela/sq meter or nit, or US system, footlambert (fL)</p>

<p>aka brightness w/o subjectivity of pupil adjustment</p>

<p>how much illuminance from a lumen</p>

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9
Q

<p>Luminous intensity</p>

A

<p>solid angular flux density in a given direction</p>

<p>measured in candlepower or candelas</p>

<p>how much radiant energy, non geometrically defined</p>

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10
Q

<p>Illuminance targets</p>

A

<p>set by IESNA, Illuminating Engineering Society of North America</p>

<p>based on ppl 25-65 yrs old</p>

<p>for older, double values,Â</p>

<p>for younger, half the values</p>

<p>restricted overall for efficiency, set in watts/sq ft</p>

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11
Q

<p>Glare</p>

A

<p>direct (bright light source) and reflected (off a surface), aka veilng glare (reduces contrast)</p>

<p>both worse when surrounding area is dark</p>

<p>visual comfort probability (VCP) metric used to evaluate glare = percentage of viewers likely to experience discomfort</p>

<p>direct glare comes from more horizontal light (so cut off at 45 deg), reflected glare from more perpendicular (so make angles of incidence and reflection unequal)</p>

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12
Q

<p>Contrast</p>

A

<p>difference in illumination level of adjacent areas</p>

<p>means by which ppl see, vital, but must be balanced</p>

<p>should be limited to 3:1 task:adj area, 5:1 task:remote dark areas, 10:1, task:remote light areas</p>

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13
Q

<p>Uniformity & Color</p>

A

<p>uniformity = perception of light being comfortable, pleasant</p>

<p>color = light source and incident surface interactions</p>

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14
Q

<p>Light source types</p>

A

<p>incandescent lamps</p>

<p>fluorescent lamps</p>

<p>high-intensity discharge (HID) lamps</p>

<p>light-emitting diodes (LED)</p>

<p>must balance color, cost (initial & operational), efficacy (ratio of luminous flux emitted:total power input), size, operating life, ability to control output</p>

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15
Q

<p>Incandescent lamps</p>

A

<p>tungsten filament, sealed glass bulb w/ inert/noble gas, filament glows w/ electrical current</p>

<p>inexpensive, compact, easy to dim, turning on/off doesn't reduce lifespan, warm colored, lenses and reflectors easy to use</p>

<p>low efficacy, high heat production, short lifespan, not energy efficient</p>

<p>halogen lamps are incandescents (tungsten halogen lamp or quartz-halogen lamp), where filament is burned away & redeposited, burns cooler light, more uniformly, better efficacy, so, samller, longer life, butÂstill high heat (and can explode)</p>

<p>reflector lamps (R lamps) & parabolic aluminized reflector lamps (PAR lamps) used metallic backing to focus beam, either flood or narrow/spot beams (most of these outlawed for inefficiency)</p>

<p>elliptical reflector lamps (ER lamps) are more efficient, focus, then throw light, so smaller, bc less light trapped in fixture</p>

<p>low-voltage miniature reflector lamps (MR lamps), small halogen lamps</p>

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16
Q

<p>Fluorescent lamps</p>

A

<p>inert/noble gas + low-pressure mercury vapor; mercury arc formed when electricity added, creates UV light, which strikes the phosphor-coated bulb, causing fluorescence</p>

<p>have high efficacy, low cost, long life, can be dimmed, but expensive</p>

<p>too UV-ish light, large, hard to control, better for general illumination, but CFLs (compact fluorescent lamps) improve this</p>

<p>preheat lamps: do not carry current unless in use, takes awhile to produce light</p>

<p>rapid-start lamps: maintain a low-voltage current so that start time reduced to ~2 seconds</p>

<p>instant-start lamps: maintain constant voltage</p>

<p>some low-efficiency fluorescent lamps outlawed, but CFL bases (not Edison screw base, but GU-24, 2-pin base) are becoming most common energy-efficient lamp base</p>

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17
Q

<p>Ballasts</p>

A

<p>device that supplies proper start/operating/control of power/voltage</p>

<p>magnetic: (older), lam. steel plates wrapped in copper</p>

<p>electronic: solid state, operate at high frequency, less noise/heat/flicker, easier to dim</p>

<p>multilevel: to easily change lighting levels</p>

<p>energy-saving: lower current, efficient ballast design</p>

<p>ballast factor (BF) = ratio of light output w/ particular ballast to that of a reference ballast, not used directly</p>

<p>ballast efficacy factor (BEF) = ballast factor x 100, used to compare same kind, number of lamps on different ballasts</p>

<p>power factor = how effectively a ballast converts supplied power to useable power</p>

<p>rated for noise (+ A-F noisy)</p>

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18
Q

<p>High Intensity Discharge (HID) Lamps</p>

A

<p>mercury vapor: electric arc passes through high-pressure mercury vapor, produces UV + visible light, phosphors can be added to warm up light</p>

<p>metal halide: metal halides have been added, improves color & efficacy, shortens life span (most commonly used), color shifts over life span</p>

<p>high & low pressure sodium: electric arc through hot sodium vapor, tube from ceramic to resist salt corrosion, very high efficacy, long life, but very yellow light, though can be color corrected; low pressure even more efficient, but deep yellow in color</p>

<p>all use an outer bulb to protect from UV light: clear (optical control required), phosphor coated (to warm up light), diffuse (for recessed downlights in low ceilings)</p>

<p>all have significant start up and cool off times</p>

<p>ceramic metal halide (CMH): ceramic arc tube, not quartz, burns at higher temp, better color & control, better efficacy, but expensive, hard to dim, requires a ballast</p>

<p>Â</p>

<p>Â</p>

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19
Q

<p>LEDs</p>

A

<p>semiconductor, solid-state electroluminescence</p>

<p>OLEDs: organic</p>

<p>PLEDs: polymer</p>

<p>bright, long-lived, low heat, low power consumption</p>

<p>low efficacy, high cost</p>

20
Q

<p>Other lamps</p>

A

<p>neon: gas filled tubes, different colors = different gases</p>

<p>cold-cathode lamps: higher efficacy than neon, mostly white, larger tube</p>

<p>fiber optic luminaire: light conducted, often for museums, pools, near flammable storage</p>

21
Q

<p>Articulation index</p>

A

<p>measure of speech intelligibility; words read from a preset list</p>

<p>low (less than .15) desired for privacy</p>

<p>high (above .6) for presentations</p>

22
Q

<p>IIC</p>

A

<p>Impact Insulation Class, measures floor/ceiling assembly's impact sound transmission</p>

23
Q

<p>NC/NIC/NR/NRC</p>

A

<p>noise criteria: single-number ratings of acceptable background noise</p>

<p>noise isolation class: noise isolation class: single number rating of noise reduction</p>

<p>noise reduction: noise difference btwn barrier of given transmission loss</p>

<p>noise reduction coefficient: average sound absorption coefficient measured at fixed frequencies</p>

24
Q

<p>Sabin formula</p>

A

<p>relates reverberation time to a room's volume and total acoustical absorption</p>

25
Q

<p>STC/TL</p>

A

<p>sound transmission class: average of a barrier's ability to reduce sound (higher is better)</p>

<p>transmission loss: decibel difference of sound at source and sound received across barrier</p>

26
Q

<p>Sound intensity</p>

A

<p>intensity level measured in decibels (dB) goes from 0 dB to 130 dB, threshold of hearing to painful</p>

<p>intensity of sound at a given point is inversely proprotional to the square of the distance from that point</p>

27
Q

<p>Loudness</p>

A

<p>subjective, but gains of 5 dB are noticeable, 10 dB is twice as loud, 20 dB is four times as loud</p>

<p>decibels are logarithmic, so they don't add up directly</p>

<p>use the table or:</p>

<p>ILtotal = IL source = 10 log n, where n is the number of noise sources</p>

28
Q

<p>Sound transmission</p>

A

<p>thicker barriers reduce it more, less stiff barriers reduce it more (if weight is equal)</p>

<p>transmission loss is the difference between sound power falling on a barrier and sound power received on other side of barrier (not the same for all frequencies with one type of barrier, STC combines these)</p>

<p>noise reduction is difference between intensity levels in two different rooms div. by barrier, so area, and absorptive surfaces in rooms is accouted for</p>

29
Q

<p>Noise criteria curves</p>

A

<p>depends on type of space</p>

<p>low frequency noises tolerated better than high</p>

<p>some noise required for spaces to not feel dead</p>

<p>preferred noise criteria is for noises that are better than acceptable</p>

30
Q

<p>Guidelines for transmission loss</p>

A

<p>easier to block high frequency sounds</p>

<p>a wall w/0.1% open area will have max 30 dB transmission loss</p>

<p>a wall w/1.0% open are will have max 20 dB transmission loss</p>

<p>hairline cracks decrease transmission loss by 6 dB</p>

<p>a 1 sq in opening in a 100 sq ft non-absorptive wall will transmit as much sound as having no wall at all</p>

<p>fibrous insulation increases the STC, but the density of the insulation doesn't matter</p>

<p>25 STC, normal speech can be heard</p>

<p>45-50 STC, only loud sounds heard faintly</p>

31
Q

<p>Sound absorption</p>

A

<p>in free space, each doubling of distance from sound source reduces it by 6 dB, but in a room, you start to have noise reflectance</p>

<p>coefficient of absorption: ratio of sound intensity absorbed to the total sound receive by a surface</p>

<p>Âbelow 0.2 is a reflective surface, above, is absorptive, max is 1.0</p>

<p>NRC/noise reduction coefficient combines the coeff. abs. for different frequencies and materials (since those are all different)</p>

<p>NRC has been superceded by SAA/sound absorption average, which focuses on averaging only the most important frequencies</p>

32
Q

<p>Guidelines for sound absorption</p>

A

<p>average coeff. abs. for a room should be at least 0.2</p>

<p>0.5 not desirable & too expensive</p>

<p>each doubling of coeff. abs. only reduces noise by 3 dB</p>

<p>if it's going to be worth it, adding absorptive material should target a 5 dB reduction, so three times an increase from original</p>

<p>an increase of 10 times original is usu. the max possible</p>

<p>each doubling of coeff. abs. reduces reverberation times by 1/2</p>

<p>in large rooms, put abs. material on ceilings; in small rooms, put it on the walls</p>

<p>increasing abs. material will increase abs., but not very much for low frequency sounds</p>

<p>want a porous, interconnected web of voids for your material</p>

33
Q

<p>Reverberation</p>

A

<p>reverb time = the time it takes for sound to be reduced by 60 dB after source has stopped</p>

<p>1.5-1.8-3.0 sec for music auditoriums</p>

<p>0.3-0.6 for small offices or broadcast studios</p>

34
Q

A sound wave that has been reflected with sufficient magnitude and delay so that it is heard as a distinct from that transmitted directly

A

echo

35
Q

The logarithmic expression for the acoustical power at the source of a sound. Also known as acoustic power level.

A

power level (pwl)

36
Q

intensity level

A

The intensity of sound at a given location, measured in watts/ sq. meter, or more commonly in dB where the reference level is 10-12 watts/ sq. m

37
Q

The intensity of light falling on a surface usually expressed in footcandles.

A

illumination

38
Q

The amount of light emitted by a source

A

luminous intensity (I)

39
Q

The length of one complete cycle or waveform for light or sound waves.

A

wavelength

40
Q

Doppler effect

A

The change in the observed pitch of sound which occurs when the observer of the sound moves

41
Q

Phon

A

A subjective unit of loudness numerically equal to the sound pressure in decibels of a 1000-Hx tone judged by the listener to have the same loudness as the given sound.

42
Q

Free-field room

A

A room whose boundaries absorb all of the sound striking them. Also known as an anechoic room.

43
Q

The time required for the sound pressure level to decrease 60dB after the original sound stops

A

reverberation time

44
Q

A family of lamps consisting of a quartz envelope inside a glass envelope. In the quartz envelope the current causes an intense arc bt two electrodes exciting a plasma of mercury metal halide or high-pressure sodium and producing visible light.

A

HID - high-intensity discharge

45
Q

The ratio of useful light arriving at the work plane to the amount of light emitted by the source which depends on the reflectivity of different surfaces and the aspect ratios of the ceiling wall and floor cavities.

A

coefficient of utilization

46
Q

Innocuous background noise used to mast objectionable sounds.

A

white noise

ARE 5.0 PPD - Project Planning & Design (15 decks)

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