BUILDING UTILITIES 3

Sound

Sound

is the sensation perceived by the human ear resulting from rapid fluctuations in the air pressure. These fluctuations are usually created by some vibrating object which sets up longitudinal wave motion in the air

Sound level

(or energy, strength, amplitude, loudness)

Frequency

(or pitch, tone, wavelength)

Propagation

(or path, elapsed time)

Frequency

When sound includes abundant high‐pitched or treble energy, it is said to be heavy on high‐frequency content, and when sound includes abundant low pitched or bass energy, it contains ample low‐frequency content.

Sound Propagation

Direct sound decays at the same rate inside as outside, shedding six decibels per doubling of distance because the same sound energy is spread over four times the area every time the distance is doubled.

Amplitude

is determined by the magnitude of the pressure fluctuation. But the range of pressures to which our ears can respond exceeds a ratio of one to a million and the response is not linear.

Decibel

to measure differences or to measure sound (or other) amplitudes. In both cases, the choice of a logarithmic scale overcomes the problem of large numbers.

pure tone

eis vibration produced at a single frequency.

hertz (Hz)

If a surface is vibrating, the frequency of vibration is the number of cycles per second, though this is now expressed in ?

Directivity

is a measure of the directional characteristic of a sound source.

ISAAC NEWTON

on his theory of light (Guillen, 1995), published in 1675 the law of elasticity that now bears his name, in the form of a Latin anagram

CEIIINOSSSTTUV

which decoded is "Ut tensio, sic vis" (Lindsay, 1966). It established the direct relationship between stress and strain that is the basis for the formulas of linear acoustics.

Plane Wave

When corresponding wavefronts of a sound wave propagate parallel to each other then the sound wave is known as a plane sound wave e.g. the sound wave produced by a piston oscillating in a long cylinder.

diverging sound wave

is one where the sound energy is spread over a greater and greater area as the wave propagates away from the sound source.

spherical sound wave

is produced by a sound source which radiates sound energy equally in all directions e.g. a monopole source.

Progressive Wave

When there is a transfer of energy in the direction of propagation of the sound wave the wave is designated as __________________________?

standing wave

is produced by the constructive interference of two or more sound waves which gives rise to a pattern of pressure maxima and minima which is stable with time

frequency (F)

The number of cycles per second is called the

Hertz

The unit of frequency is the ?

1 Hertz

_____________ = 1 cycle/sec

period (T)

The time taken for the oscillation to repeat itself is known as the ?

Sound waves

are longitudinal waves (i.e involve oscillations parallel to the direction of the wave travel) that propagates through a medium (e.g. air, water, iron)

Speed of Sound

The speed of any mechanical wave depends on the both the inertial property of the medium (stokes kinetic energy) and the elastic property (store potential energy).

free-field conditions

Sound Waves from a point source outdoors with no obstructions called ____________________ are virtually spherical and expand outward from the source as shown below

intensity

from a point source outdoors at a distance d away is the sound power of the source divided by the total spherical area And^ of the sound wave at the distance of interest.

sabins

The total absorption in a room, the "room constant," measured in a unit called ?

noise reduction coefficient NRC

is the arithmetic average, rounded off to the nearest multiple of 0.05, of the sound absorption coefficients a's at 250, 500, 1000, and 2000 Hz for a specific material and mounting condition.

Reverberation Time

Defined as the persistence of sound.

steeply sloped seating

When _________________ is used, the sound level outdoors falls off primarily with distance. An overhead sound-reflecting panel or ceiling can provide reflected sound to reinforce the direct sound.

hard, sound-reflecting enclosure

outdoors near the sound source can greatly improve listening conditions by reflecting sound energy toward the audience and by shielding the audience from noise sources located behind the enclosure.

Sight lines

are normally drawn to converge at a point on stage called the arrival point of sight APS. Audiences should be able to hear and to see clearly and comfortably to fully perceive the intended effects of performances.

ray diagram

is an acoustical analogy to the specular reflection of light where the angle of incidence ∠i of an impinging sound wave equals the angle of reflection ∠r, with angles measured from the perpendicular to the surface.

Reflection

is the return of a sound wave from a surface. (x > 4 λ)

Diffusion

is the scattering or random redistribution of a sound wave from a surface. It occurs when the surface depths of hardsurfaced materials are comparable to the wavelengths of the sound. (x = λ)

Diffraction

is the bending or "flowing" of a sound wave around an object or through an opening. (x < λ)

Concave Reflector

can focus sound, causing hot spots and echoes in the audience seating area.

Flat Reflector

can effectively distribute reflected sound.

Convex Reflector

can be most effective as sound-distributing forms. The reflected sound energy from convex surfaces diverges, enhancing diffusion, which is highly desirable for music listening.

Echoes

The distinct repetition of the original sound and is sufficiently loud to be clearly heard above the general reverberation and background noise in a space.

Rear Wall Echo Control Treatment

A flat, sound-reflecting rear wall can produce echoes or unwanted, long delayed reflections in medium to large auditoriums.

Flutter Echo

Repetitive interreflection of sound energy between opposing parallel or concave sound-reflecting surfaces.

Pitched-Rood Flutter Echo

The echo phenomenon which occur in rooms with non-parallel walls.

Audible resonance

is the emphasis of sound energy at particular frequencies. It can occur in small rooms entirely finished with sound-reflecting materials when the dimensional ratios are whole numbers (e.g., cube).

Reflection

from a finite surface depends on the relationship between the size of the reflector and the wavelength of sound.

diffraction

A textured surface will provide some scattering of sound, but the degree of texturing must be high for efficient scattering. The general principle is that the deeper the scattering treatment, the lower the frequency down to which the surface will scatter sound.

absorption

removes acoustic energy. there are three possible mechanisms: porous absorption, panel absorption and helmholtz resonance. porous absorption, as already mentioned, occurs with any porous material.

Daylighting

is an excellent light source for almost all interior spaces. It is best for offices, schools, and workspaces requiring a lot of light and for public spaces such as malls, airports, and institutions.

Windows, skylights, and other forms of fenestration

are used to bring daylight into the interiors of buildings.

Daylight

is highly desirable as a light source because people respond positively to it.

Daylighting

is the complete process of designing buildings to utilize natural light to its fullest.

Top lighting

behaves as direct electric lighting does by radiating light downward.

Side lighting

employs vertical fenestration (usually windows) to introduce natural light.

Windows

have the advantage of providing both daylight to the interior and a view out.

Clerestory windows

are strictly a narrow strip of windows high up on the wall.

Rooflights

are a glazed opening in the roof of a building.

Atria

have become an increasingly popular feature of buildings. ____________ are often used to light central circulation or social area by daylight admitted through a glass roof or wall.

Remote distribution

all collect daylight and sunlight in some way and transmit in through a shaft or pipe by reflection to a distribution point in the space.

Borrowed light

is a term used to describe the lighting of an enclosed internal space through a window that connects to an adjacent daylit space

visual problems

are glare and veiling reflections. Glare is caused by a direct view of either the sun or the bright sky.

thermal problems

Daylight admitted to a building represents a heat load. In winter this may be useful but in summer it can represent an additional cooling load.

privacy problem

Extensively glazed buildings can present _____________, particularly on the ground floor. Concerns about privacy can lead to blinds being closed at all times with a consequent lack of daylight and view out.

flame of fire

first artificial light source was the ?

Incandescent gas light

was accompanied practically simultaneously by the development of electric arc and incandescent lamps, which were joined at the end of the 19th century by discharge lamps.

"phlogistos"

Until the birth of modern chemistry, the belief laid down by the ancient Greeks was taken to be true: during the burning process, a substance called _______________ was released

combustion

It was only through Lavoisier's experiments that it became clear that _________________ was a form of chemical action and that the flame was dependent on the presence of air.

Francois Argand

constructed a lamp that was to be named after him, the Argand lamp.

Mirrors

are known to have been used by ancient Greeks and Romans and the theory behind their application set down in writing.

optical lenses

At the turn of the first millennium, there were a number of theoretical works in Arabia and China concerning the effect of ?

the first telescopes

were designed by Dutch lens grinders.

microscopes and projector equipment

n the 17th century these instruments were then perfected by Galileo, Kepler and Newton; ______________________ were then constructed.

Huygens

saw light as a phenomenon comprising waves.

photometrics

With the development of _______________ - the theory of how to measure light - and illuminances - through Boguer and Lambert in the 18th century, the most essential scientific principles for workable lighting engineering were established.

Augustin Jean Fresnel

developed a composite system of stepped lens and prismatic rings which could be made large enough to concentrate the light from lighthouses; this construction was also first installed in Cordouan.

Incandescence

When an object is heated to a high temperature, the atoms within the material become excited by the many interactions between them and energy is radiated in a continuous spectrum.

electric discharge

is an electric current that flows through a gas.

Electroluminescence S

some materials will convert electricity into light directly

Luminescence

The process involves a material absorbing radiation and then re-emitting light.

Radioluminescence

This occurs in a similar manner to luminescence, but the primary source of the activation energy is particles or gamma rays emitted by a decaying nucleus of a radioactive atom.

cathodoluminescence

he energy driving the phosphor is an electron that has been accelerated away from a cathode. This process is the means by which light is generated in a cathode ray tube.

Chemiluminescence

Some chemical reactions can produce light directly, not via the heat the reaction creates. The process is used by some living organisms to generate light; the best-known example being the glow worm.

Thermoluminescence

This is exhibited by some materials when they are heated. The materials give out much more light than would be expected due to black body radiation. The best-known practical use of the method of light production is the mantle used in some types of gas lamps.

Skylight

is the light from the sun which is scattered in the atmosphere. The distribution and amount of light received at ground level is dependent on atmospheric conditions.

incandescent lamp

is operated by heating a filament in the lamp to a high temperature, so that it emits light. The hotter the filament, the whiter the light.

A and R lamps

Standard incandescent lamps, such as ______________, are still commonly used in residences, hotels and motels, and some retail environments where a residential- like quality is desired.

Tungsten-halogen lamps (also called TH or simply halogen lamps)

give off whiter light and last longer than standard incandescent lamps.

MR16 and PAR (Parabolic Aluminized Reflector Lamp) low voltage lamps

are commonly used in museums and galleries, residences, landscape lighting, and other applications where a modest amount of light and excellent beam control are called for.

Fluorescent lamps

work by generating ultraviolet radiation in a discharge in low pressure mercury vapor.

Fluorescent and compact fluorescent lamps

provide good energy efficiency, good to excellent color, dimming, and many other features expected of modern light sources.

High Pressure Mercury

In this type of lamp, a discharge takes place in a quartz discharge tube containing mercury vapor at high pressure (2 to 10 atmospheres).

Metal halide lamps

were developed as a way of improving the performance of high-pressure mercury lamps in terms of their color appearance and light output.

Low pressure sodium lamps

are similar in many ways to fluorescent lamps as they are both low pressure discharge lamps.

high pressure sodium lamp

generates light in a discharge through sodium vapor at high pressure. As the vapor pressure of sodium in a lamp rises the spectrum at first broadens and then it splits in two with a gap appearing at about 586 nm.

Induction lamps

are essentially gas discharge lamps that do not have electrodes. Instead, the electric field in the lamp is induced by an induction coil that is operating at high frequency.

Light Emitting Diode (LEDs) a

are available in a wide variety of sizes, colors and power ratings and development is proceeding at a rapid rate. _____________ generally have a long life and may last up to 100,000 hours.

constancy

One of the most important tasks of perception is to differentiate between constant objects and changes in our surroundings in the continuously changing shapes and distribution of brightness of the image on the retina.

law of gestalt

The process of identifying this object in the profusion of continuously changing stimuli on the retina is no less problematic than the perception of objects.

luminous flux

describes the quantity of light emitted by a light source.

luminous efficiency

is the ratio of the luminous flux to the electrical power consumed (lm/W). It is a measure of a light source's economic efficiency.

luminous intensity

describes the quantity of light that is radiated in a particular direction. This is a useful measurement for directive lighting elements such as reflectors. It is represented by the luminous intensity distribution curve (LDC).