amplified(jukebox)

unamplified (violins- classical like guitar etc - natural sound)

support desirable sound

minimize undesirable sound

Room Acoustics - does it reflect/ absorb

Sound Isolation - 3 dimensions

Mechanical Noise Control

Audio Systems- electroacoustics

Architectural Acoustics

Natural Acoustics

Electroacoustics

Architects

Physicists

Mechanical Engineers

Electrical Engineers

Musicians

Actors

sound is a wave in a medium (usually air)

speed of sound is 1130 ft/s

1 msec= 1 foot not as fast as light

45-50 feet is a good amount of space to be reflected

Frequency x Wavelength = Velocity

High Frequency = Short Wavelength

Low Frequency = Long Wavelength

20,000 HZ = 1/2 inch = upper limit of hearing

20 HZ = 56 feet = lower limit of hearing

requires mass - to hold low frequencies it must be massive,

mass more airspace

must also take into account juncture in concrete flow-

70db = 70 db

73 db = 80 db

a small increase or decrease in pressure is a large increase or decrease in the loudness perceived

Sound scatters and doesn't bounce straight back

low vs high

short wavelengths- small texture differences

long wavelengths large diffusion with convex and big angles- like the ceiling at Krannert

random differences in depth is better for diffusion rather than repetitive patterns

Room Size - dependent on occupancy

Room Shape - helps it diffuse- shoebox - general proportions

Surface materials- reflect or absorb

Surface shaping - diffuses and directs

Hundreds of Random Reflections

Gradual Dying Away

Can be good or bad

Dry, Dead is 1.0 seconds

Live 2.0 seconds

Single late reflection

louder than reverberation

arrives more than 50 msec after the direct sound

Confusing avoid them

Multiple late reflections

Sound trapped in repetitive pattern

lasts longer than reverberation

Organist "I want to swim in sound"

Violinist "Very live and very clear, please"

Audio Designer: "The only good acoustic is a dead accoustic"

More Room Volume = longer reverberation

More Absorption = shorter reverberation

What you would get back from the room

pretty constant angle good

echoes go up and down

Long Reverberation 2.2 seconds

Support around orchestra

Diffuse response from room

Moderate Reverberation 1.6 seconds

Support around the Proscenium

Strong response from room

Short Reverberation 1.2 seconds

Amplification

No Response from the room

quiet background noise

no distracting intrusions

no strong echoes

no flutter

Support around musicians

Support around audience

Room Response

Longer Reverberation

for orchestra

ceiling is important to reflect back to audiences

Carefully aimed speakers - critical

must have space for loud speakers

Absolutely no echoes

Shorter reverberation

Keeping outside noise outside

noise and vibration

DEPENDS ON

Energy at source

Effectiveness of barrier

Background noise in room

Making source quieter

Increasing background noise

Increasing transmission loss

Air Tightness - gaskets sealents

Mass 18" concrete walls and roof

Seperation -vestibules at entries -double slab roof -surrounding building -isolation joint (rubber isolation pads)

Room Acoustics

Sound Isolation

Noise Control

- A single number rating. A simplification of the amount of sound that is audible within a space

-Design Target

Higher the number the louder the noise

Classrooms RC-30, Church RC-25, Concert Hall RC-15

NC  /  RC   / dB (A) - often used for outside noise

Sound Power- watts- impractical

Sound Pressure (decibels)- log of power

Manifests as

"Structure Borne"

Air Borne"

Duct Borne"

Sound Absorption

measure of the amount of sound absorbed by a material in a particular installation

Sound Transmission Coefficient

amount of sound that can pass through a structure or device