BU 3

• Acoustics


  The science of sound and vibration which refers to the stress fluctuations as well as waves in a material medium
• Acoustics


  The art and science of designing a room or building which ensures both comfort and communication, and provides special features as the purpose and use of the structure requires
• Acoustics


  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
• Common elements of acoustic situations

  • Source
  • Transmission path
  • Receiver
• Types of acoustics


  • Psycho acoustics
  • Environmental acoustics
  • Architectural acoustics / Room acoustics
  • Landscape acoustics
  • Electro acoustics
  • Sonics
• Sound


  A physical wave, or a mechanical vibration, or simply a series of pressure variations in an elastic medium
• Sources of sound


  • Speech
  • Music
  • Noise
• Types of sound


  • Wanted
  • Unwanted
• Properties of sound


  • Sound must always have a source, a path, and a receiver
  • Sound travels at 1130 ft. per second or 344 meters per second at normal room temperature (68°F)
  • Sound travels faster in denser media
  • Sound 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
• 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
• 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
• Acoustics


  The science of sound and vibration which refers to the stress fluctuations as well as waves in a material medium
• Pitch


  The attribute of an auditory system which enables us to pinpoint sounds on a scale extending from high to low frequency
• Architectural acoustics / Room acoustics


  The technology of designing spaces, structures, and mechanical systems to meet hearing needs
• Tone


  Sound sensation having pitch
• Types of acoustics


  • Psycho acoustics
  • Environmental acoustics
  • Architectural acoustics / Room acoustics
  • Landscape acoustics
  • Electro acoustics
  • Sonics
• Directionality of sound sources

  • 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
• Sound


  A physical wave, or a mechanical vibration, or simply a series of pressure variations in an elastic medium
• Natural elements that affect sound

  • Temperature
  • Clouds
  • Wind
  • Bodies of water
• Sources of sound


  • Speech
  • Music
  • Noise
• 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
• Types of sound


  • Wanted
  • Unwanted
• 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
• Properties of sound


  • Sound must always have a source, a path, and a receiver
  • Sound travels at 1130 ft. per second or 344 meters per second at normal room temperature
  • Sound intensity diminishes inversely as the square of the distance
  • Decibel is the unit which sound intensity is defined for architectural purposes
  • Sound pressure is the fluctuation in the atmospheric pressure caused by the vibration of air particles due to sound wave
  • Wavelength is the distance a sound wave travels during each complete cycle of vibration
  • Loudness is the subjective attribute of an auditory sensation in terms of which sound may be ordered on a scale of soft to loud
  • Threshold of audibility is the minimum intensity that is capable of evoking an auditory sensation in the ear
  • Threshold of pain is the minimum sound pressure level which stimulates the ear to a point which is painful
  • Frequency is the number of displacements or oscillations that a particle undergoes in one (1) second
  • Pitch is the subjective response of human hearing to sound frequency
  • Tone is a sound sensation having pitch
  • Directionality of sound sources is the way in which sound is distributed in a region free from reflecting surfaces
• Sound absorption


  • Sound waves absorbed into a material upon contact
  • Change of sound energy into some other form
• Natural elements that affect sound

  • Temperature
  • Clouds
  • Wind
  • Bodies of water
• Sound diffusion


  Occurs when sound waves are dispersed equally in a room
• Characteristics of sound


  • Sound reflection
  • Sound absorption
  • Sound diffusion
  • Sound diffraction
  • Sound refraction
  • Sound transmission
  • Flanking transmission
  • Direct transmission
• Sound diffraction


  Acoustical phenomenon which causes sound waves to be bent or scattered around such obstacles as corners, columns, walls, beams, etc.
• The Wealth of Nations was written in 1776
• Marginal utility


  The additional utility (satisfaction) gained from the consumption of an additional product
• Sound refraction


  Change of sound wave direction as it moves from one medium to another of different density
• If you add up marginal utility for each unit you get total utility