BUILDING UTILITIES 3 ARCHITECTURAL ACOUSTICS and LIGHTING
ACOUSTICS
ACOUSTICS -
the science of sound and vibration which refers to the stress fluctuations as well as waves in a material medium
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the art and science of designing a room or building which insures both comfort and communication, and provides special features as the purpose and use of the structure requires
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the science of sound phenomena in buildings dealing with the production, transmission, and absorption of sound in order to secure the distinct conditions in every part of the building or room
All acoustic situations have three common elements:
SOURCE can be made louder or more quiet
TRANSMISSION PATH the path can be made to transmit more or less sound
RECEIVER
the listener ; assumed to have a pair of healthy young ears with a detection range of 20 to 20,000 Hz.
ACOUSTICS TYPES OF ACOUSTICS
PHSYCO ACOUSTICS deals with the reaction of human beings to audible sound
ENVIRONMENTAL ACOUSTICS
deals with the effects of the environment upon audible sound waves
ARCHITECTURAL ACOUSTICS / ROOM ACOUSTICS may be defined as the technology of designing spaces, structures, and mechanical systems to meet hearing needs.
LANDSCAPE ACOUSTICS
ELECTRO ACOUSTICS deals with the generation and detection of audible sound waves
SONICS
deals with the technical application of mechanical waves in basic scientific research, industry, and medicine.
ACOUSTICS
SOUND -
Is a physical wave, or a mechanical vibration, or simply a series of pressure variations in an elastic medium. -
For airborne sound – the medium is air
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For Structure-borne sound – the media are concrete, steel, wood, glass and a combination of all of these
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Any vibratory motion of bodies, the transmission of these vibrations in a medium, and the sensation produced on the human auditory mechanism
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An alteration in pressure (particle displacement in velocity) projected and propagated in an elastic material
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Also Audible signals
SOURCES OF SOUND
SPEECH – produced by human voice
MUSIC – produced by an instrument
NOISE – produced by impact, by vibrating bodies, even by speech or music
ACOUSTICS
ACOUSTICS
SOUND TYPES OF SOUND
WANTED – sound heard as perfectly as possible at the right level or loudness without pain or strain
UNWANTED – sound which entails an annoyance factor
PROPERTIES OF SOUND
Sound must always have a source, a path, and a receiver.
SPEED
- sound travels at 1130 ft. per second. Or 344 meters per second at normal room temperature (68°F) - sound travels faster in denser media
INTENSITY - rate at which sound energy is being transmitted - intensity diminishes inversely as the square of the distance
Decibel – the unit which sound intensity is defined for architectural purposes
Decibel-meter – instrument by which sound intensity is measured
ACOUSTICS
SOUND PROPERTIES OF SOUND
SOUND PRESSURE - the fluctuation in the atmospheric pressure caused by the vibration of air particles due to sound wave
WAVELENGTH - the distance a sound wave travels during each complete cycle of vibration measured in meters or feet
LOUDNESS
- subjective attribute of an auditory sensation in terms of which sound may be ordered on a scale of soft to loud
THRESHOLD OF AUDIBILITY - minimum intensity that is capable of evoking an auditory sensation in the ear
THRESHOLD OF PAIN - minimum sound pressure level which stimulates the ear to a point which is painful
ACOUSTICS
SOUND PROPERTIES OF SOUND
FREQUENCY - the number of displacements or oscillations that a particle undergoes in one (1) second
HERTZ – unit measure of frequency; numerically equal to cycles per second
PITCH - the attribute of an auditory system which enables us to pinpoint sounds on a scale extending from hight o low frequency - subjective response of human hearing to sound frequency
TONE - sound sensation having pitch
DIRECTIONALITY OF SOUND SOURCES - the way in which it sound is distributed in a region free from reflecting surfaces
- sound sources radiate sound waves in all directions; - radiation pattern varies with the frequency - high frequency sounds are more pronounced along the longitudinal axis of the sound source.
ACOUSTICS
ACOUSTICS
SOUND NATURAL ELEMENTS THAT AFFECT SOUND
TEMPERATURE - particles of sound tend to follow cold air
CLOUDS - if heavy, clouds can act as a reflecting surface
WIND - may change the direction of sound
BODIES OF WATER - can also act as a reflecting surface
CHARACTERISTICS OF SOUND
SOUND REFLECTION – sound reflected off a surface, usually one which is hard, rigid and / or flat
FLAT SURFACE – uniform reflection
CONVEX SURFACE – sound dispersion
CONCAVE SURFACE – sound concentration
As a sound wave strikes an interface between two media with normal incidence (i.e orthogonal or perpendicular to the direction of the wave) sound can only either be reflected or transmitted
ACOUSTICS
CONCAVE SURFACE – sound concentration CONVEX SURFACE – sound dispersion
FLAT SURFACE – uniform reflection
SOUND REFLECTION
ACOUSTICS
USEFUL CEILING REFLECTIONS
SOUND REFLECTION
ACOUSTICS
USEFUL CEILING REFLECTIONS
SOUND REFLECTION
ACOUSTICS
SOUND REFLECTION
ACOUSTICS
SOUND CHARACTERISTICS OF SOUND
SOUND ABSORPTION - sound waves absorbed into a material upon contact - change of sound energy into some other form
SOUND DIFFUSION- occurs when sound waves are dispersed equally in a room
SOUND DIFFRACTION - acoustical phenomenon which causes sound waves to be bent or scattered around such obstacles as corners, columns, walls, beams, etc.
SOUND DIFFRACTION
ACOUSTICS
SOUND DIFFRACTION
ACOUSTICS
SOUND DIFFRACTION
ACOUSTICS
SOUND DIFFRACTION
ACOUSTICS
SOUND CHARACTERISTICS OF SOUND
SOUND REFRACTION - change of sound wave direction as it moves from one medium to another of different density
ACOUSTICS
SOUND CHARACTERISTICS OF SOUND
SOUND TRANSMISSION - sound which penetrates through surface
FLANKING TRANSMISSION - sound travelling along parts of the building other than the common wall or floor.
DIRECT TRANSMISSION - sound coming through the common wall or floor
ACOUSTICS
ACOUSTICS
BEHAVIOR OF SOUND IN AN ENCLOSED SPACE 1.
INCIDENT or DIRECT SOUND
2.
REFLECTED SOUND
3.
SOUND ABSORBED BY SURFACE TREATMENT
4.
DIFFUSED SOUND
5.
DIFFRACTED SOUND
6.
TRANSMITTED SOUND
7.
SOUND DISSIPATED WITHIN THE STRUCTURE
8.
SOUND CONDUCTED BY THE STRUCTURE
