Term
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Definition
o The sensation that is stimulated in our ears by radiant energy transmitted as pressure waves through the air another medium
o Is induced through the ear by means of waves of varying air pressure emanating from a vibrating source. |
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Term
| three things that must be present for sound to exist |
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Definition
o a source,
o a transmission path, and
o a receiver. |
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Term
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Definition
| o The branch of physics that deals with the production, control, transmission, reception and effects of sound. |
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Term
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Definition
| is the planning, shaping, finishing and furnishing of an enclosed space to establish an acoustic environment necessary for the distinct hearing of speech or musical sounds. |
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Term
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Definition
o A vibrating object radiates sound waves outward from the source equally in all directions until they hit a surface that either reflects or absorbs them.
o These waves have peaks and valleys. |
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Term
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Definition
o wavelength = one cycle, distance between peak to peak
o frequency = cycles or oscillations per second
o amplitude = power or pressure of wave |
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Term
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Definition
| o Whether we perceive sound as high or low depends on it frequency |
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Term
| Sound Perception - 3 measurements |
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Definition
o hertz = the measure of a sound wave’s frequency(1 Hz = 1 cycle per second)
o pitch = the “perception” of sound quality (high pitch or low pitch)
o loudness = a measure of the power of sound (dB) |
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Term
| does a cello or violin have a deeper pitch? |
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Definition
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Term
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Definition
When a sound wave strikes a surface that is large compared to the wavelength, a portion of the sound energy is reflected and a portion is absorbed.
Hard and rigid surface reflect more sound. |
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Term
| Do reflected sound leave the surface at an angle equal to the angle at which it strikes? |
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Definition
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Term
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Definition
• The persistence of sound after the source of the sound has ceased.
• Reverberation affects the intelligibility of speech and the quality of music. |
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Term
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Definition
the amount of time that sound bounces around a room before dying out to inaudible levels.
• Sound absorbing materials decrease reverberation time.
• Quality of sound is controlled by amount and type of absorptive or reflective finishes in a space. |
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Term
| In a large room, is reverberation longer or shorter and why? |
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Definition
| longer because there is a larger volume and longer distances to cover |
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Term
| Does music benefit from shorter or longer reverberation times? |
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Definition
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Term
| does speech benefit from longer or shorter reverberation times? |
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Definition
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Term
| Attenuation and when does it occur |
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Definition
• The decrease in energy or pressure for each unit area of a sound wave.
• This occurs as the distance between sound and its source increases as a result of absorption, scattering, or spreading in three dimensions. |
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Term
| natural sound reinforcement |
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Definition
| • The amplification of sound being heard from various reflections as well as directly from the source. |
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Term
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Definition
| • When repetitions of a sound are produced by reflection of sound waves from a surface, loud enough and received late enough to be perceived as distinct from the source. |
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Term
| when does a clear echo occur? |
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Definition
| • A clear echo is caused when reflected sound reaches a listener from 50-80 milliseconds after the listener has heard the direct sound. |
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Term
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Definition
| careful planning of the room’s geometry, or selective use of absorptive surfaces. |
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Term
| where could the absorbing sound energy in echoes be redirected? |
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Definition
| places where it become useful reinforcement |
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Term
| It is useful to allow____________ along short paths, while __________ at excessive distances. |
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Definition
| • It is useful to allow natural sound reinforcement along short paths, while absorbing sound at excessive distances. |
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Term
| what is flutter and when do they usually occur and how can they be avoided? |
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Definition
• The effect when sound waves are rapidly reflected back and forth between two parallel flat or concave surfaces.
• Usually occurs between shallow domes and hard flat surfaces.
• The remedy is to change the shape of the reflecting surfaces or change their parallel relationship. Adding absorptive material is another alternative. |
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Term
| what are standing waves and how can they be improved? |
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Definition
• Perceived points of quiet and of maximum sound within a room.
• Can be improved by slightly tilting or skewing two parallel walls. |
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Term
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Definition
| • Sounds that are reflected from a concave surface converging at a single point. |
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Term
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Definition
| • The reflection of sound along a curved surface from a source near the surface. |
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Term
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Definition
| • When sound is absorbed, the sound energy flows through the absorptive material as heat. |
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Term
| ______ sound frequencies require ______ sound absorptive material. |
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Definition
| Lower sound frequencies require thicker sound absorptive material. |
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Term
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Definition
| • When two separate sources of sound are perceived simultaneously, those sounds tend to obscure each other. |
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Term
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Definition
| • When two separate sources of sound are perceived simultaneously, those sounds tend to obscure each other. |
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Term
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Definition
• Unwanted sound.
• Very subjective… |
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Term
| Lessons from Fogg Lecture Hall |
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Definition
• …the difficulty to remedy a space that is initially built with poor proportions
• …an example of how inexact the process of acoustic design can be |
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Term
| What is the role of the designer? |
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Definition
o To recognize potential problems and take appropriate 3steps to solve them.
• design integration
• careful planning
• get a specialist
o By limiting sources of noise, the amount of necessary acoustic treatment can be reduced.
• For Existing Buildings
Define the character of the sound problem.
• For New Buildings
Imagine what noise sources can be anticipated.
o Remember, all parts of the building and its surfaces are potential paths for sound travel.
o Where loud noise is a special problem or where the quality of interior sound is critical, call in an expert. |
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Term
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Definition
o Use appropriate interior spaces as buffers
• mechanical
• service areas
• utility areas
o Since sound energy lessens in intensity as it disperses over a wide area, outdoor sound control starts with placing the building as far away from the noise source as possible. |
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Term
| Massive materials and list 5 |
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Definition
o Use of Massive Materials prevents outside noise from carrying inside the building
• brick
• aerated concrete
• CMUs
• porous stone
• (plywood) |
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Term
| What are the two decision made by you have a great impact on controlling interior sound? |
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Definition
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Term
| Acoustic Attenuation and 4 means of doing it |
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Definition
o Acoustic attenuation is the reduction of the magnitude of a sound signal
separation of sound source and listener
enclosing the source to isolate the sound
absorbing the sound with materials that change the sound energy to heat
canceling sound waves by electronic means |
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Term
| three important aspects of spatial design that affects the sound levels |
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Definition
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Term
| Two means for specifying appropriate materials |
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Definition
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Term
| acoustically transparent surfaces |
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Definition
o Acoustically absorbent materials (usually panels) are often covered with perforated metal or other materials for protection and stiffness.
• holes in metal/surface material allow sound to pass through and be absorbed by the inner panel
• smaller holes allow higher frequencies to pass through to the absorptive panel |
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Term
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Definition
diffuse acoustic field
• a condition in which the sound level of sound reflected from the walls and other obstructions becomes uniform throughout the room
• an ideal sound situation
• no echo
• convex surface diffuses sound more uniformly
• important for music |
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Term
| Three Principles for Reducing Noise |
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Definition
First Principle: reduce noise at its source
• proper planning and placement of mechanical equipment and spaces prone to noise
Second Principle: reduce noise transmission from point to point along transmission path
• Selecting appropriate construction methods and materials
Third Principle: acoustic treatment of the space (interior design)
• Spatial design and finish selections
Geometry
Materials
Additive measures |
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Term
| four additive measures for reducing sound |
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Definition
Silencers
Bafflers or mufflers
Diffusers
Cancellers |
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Term
| Reflective materials and name 3 |
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Definition
o Materials that DON’T absorb sound or absorb very little sound
• painted concrete
• resilient flooring
• glass |
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Term
| Spaces where it is very important to pay attention to acoustics |
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Definition
opera houses
concert halls
theaters
classrooms
lecture halls
libraries
stadiums |
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Term
| what do acoustical consultants do? (4) |
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Definition
Assist in selection of materials such as interior surface materials
Detail construction components
Design and specify sound and communication systems
Detail for noise and vibration controls in mechanical systems |
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Term
| outside/exterior examples of blocking noise (4) |
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Definition
Earth berms/terrain between highways and buildings
Heavy concrete walls to block/absorb sound
Dense plantings of trees and shrubs helps diffuse and scatter sound
Grass and groundcover provides sound absorption |
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Term
| combating interior noise and 3 examples |
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Definition
o Since sound energy lessens in intensity as it disperses over a wide area, outdoor sound control starts with placing the building as far away from the noise source as possible.
• Inside/Interior Examples
Mechanical, service, utility areas as sound buffers
Locate areas with higher noise levels on the nosier side of the building
Quiet spaces should be located as far as possible from exterior noise sources |
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Term
| why is acoustic attenuation a problem? |
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Definition
• Weight of building materials have been reduced to reduce construction costs
• Lighter building materials transmit sound more easily through the structure
• Offices are smaller and more densely packed with people
• Open office plans eliminate barriers to sound creating challenges for speech
• privacy
• Mechanical system noise |
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Term
| what is the coefficient of absorption |
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Definition
| a material's sound absorption characteristic |
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Term
| the _____ the absorption coefficient the _____ efficiently materials can absorb sounds |
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Definition
| • The larger the absorption coefficient the more efficiently materials can absorb sound |
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Term
| 4 factors that affects how sound behaves in a room |
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Definition
• Room size
• Room shape
• Room proportion
• Room’s surface materials
(absorptive, diffusing, reflecting, diffracting) |
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Term
| 4 ways noise is regulated through codes |
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Definition
• City and town ordinances and regulations
• Public health agencies (OSHA)
• Building codes (IBC)
• Material regulating bodies (ASTM, ANSI) |
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Term
Interior noise control and reduction
and 4 ways to do it |
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Definition
o The acoustic treatment of a space starts with reducing the source of the noise, unwanted sound reflections as well as controlling speech privacy and sound reverberation.
o To reduce noise within a building…
• reduce it at the source
• intercept it
• isolate it
• absorb it (interior materials and finishes) |
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Term
what controls the noise levels within the space?
what controls the transmission of noise between spaces? |
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Definition
the contents of the space
the structure of the building |
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Term
| o When all of the sound energy striking the material is absorbed, and none of it is reflected, the absorption coefficient is what? |
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Definition
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Term
| When all of the sound energy striking the material is reflected, and none of it is absorbed, the absorption coefficient is what? |
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Definition
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Term
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Definition
o NRC = Noise Reduction Coefficient
• The NRC rating is an average of how absorptive a material is at four frequencies (250, 500, 1000 and 2000 Hz).
• Because this rating is an average, two materials with the same rating might not perform the same in identical applications. |
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