Environmental Technology III Acoustics

Room Acoustics
The control of sound which originates within an enclosure
Sound Transmission
The control of sound between or into an enclosure
frequency
vibration cycles per second (measured in Hz) Determines sound pitch.
Amplitude
volume
wave length
distance between identical points on a wave
decibel
units of measure for sound intensity.
velocity
rate at which sound travels through a conductor
direct sound
segment of the overall sound wave that travels in a direct line to the listeners ears
diffusion
sending a sound wave in many different directions to reduce volume
reflection
sound bouncing off an object. shape of the space determines the sound path.
diffraction
sound can bend around objects of travel through small openings
reverberation
the perpetuation of reflected sound within a space after the source has ceased
reverberation time (in seconds)
(.05 X Volume of Room(ft^3))/sabins
absorption is measured in
sabins
sabin
sound absorption of one squarefoot of material.
the perfect absorptive surface would be
1.0
Good Acoustical Characteristics
reflective surfaces towards the front of the space.
absorptive surfaces towards the rear.
Acoustical environments are either:
Live or Dead
A Live acoustical environment is
highly reflective
A Dead acoustical environment is
highly absorptive
acoustic resonance
acoustic system the absorbs more energy at certain frequencies
sound conditioning is
creating a good acoustical environment for occupant.
should be shielded from annoyance and distractions.
background noise
certain amounts of continuous sound can be tolerated (or welcomed) before it becomes noise
preferred noise criterion
noise levels above 60db are not recommended
Minimizing background noise
masking, sound isolation
controlling airborn sound
mass (weight), isolation (decoupling),absorption
flanking paths
continuous rigid connections between spaces that allow unwanted noise to be transferred, such as: plumbing pipes, air ducts, electrical conduit
STC (Sound Transmission Class)
Rating of how well a building partition dims airborn sound
NRC (Noise Reduction Coefficient)
amount of sound energy absorbed upon striking a particular surface
CAC (Ceiling Attenuation Class)
Measure of the sound transmission loss as noise travels between rooms. (Essentially, it is the ability of a ceiling panel to block sound between rooms.)
masking
using more desirable sounds to cover up less desirable sound. creating additional background noise.
sound isolation
function of good acoustical design.
sound barriers remove
10-20db from noise level