This document provides an overview of architectural acoustics. It defines acoustics as the science dealing with the production, control, transmission, reception, and effects of sound. It discusses how different materials reflect, transmit, or absorb sound waves. Hard surfaces like tile and wood tend to reflect sound waves and cause echoes, while soft surfaces like textiles and insulation absorb sound waves. It then discusses some pioneers in acoustics like Pythagoras and how the early Greek civilization was concerned with acoustic design of theaters. Finally, it briefly touches on topics like resonance, standing waves, interference, and provides some examples of acoustic panels.

1. UNIT-1
ARCHITECTURAL ACOUSTICS

2. • “a science that deals with the production, control,
transmission, reception, and effects of sound.”
Acoustics
• Sound is reflected, transmitted, or absorbed by the
materials it encounters.
• Soft surfaces, such as textiles, and batt insulation, tend
to absorb sound waves, preventing them from further
motion.
• Hard surfaces, such as ceramic tile, gypsum board, or
wood, tend to reflect sound waves, causing ‘echo’.
Reverberation is the term used to describe sound waves
that are reflected off of surfaces.

3. • Sound is a mechanical wave and therefore requires a
medium in which it can travel.
• Acoustics is classically divided into sound and
vibration.
• Sound refers to waveforms traveling through a fluid
medium such as air
• Vibration describes energy transmitted through
denser materials such as wood, steel, stone, dirt,
drywall or anything besides a fluid.
• It is not heard as much as felt, due to its extremely
low frequency, which is below the range of most
human hearing.
Acoustics: sound

4. P I O N E E R S
• Greek philosopher and mathematician.
•
• Sought to explain the nature of all things in
mathematical terms.
•
• His greatest scientific studies were of
sound: “He found that the strings of
musical instruments delivered sound of
higher pitch as they were made shorter.”
• He discovered the relationship of pitch with
string length and recognised “if one string
was twice the length of another, the sound
it emitted was just an octave lower.”

5. POLYCLEITUS THEYOUNGER active 360 BC
• Greek architect and sculptor
Designed the famous open-air
theatre at Epidaurus which is the
best preserved, and
generally considered to be the
most beautiful, of surviving Greek
Theatres. It took thirty years to
build: “Its vast
symmetrical auditorium, rather
more than semi-circular in plan, is
divided by radiating stairways and,
unusually,
has two distinct slopes, the upper
being steeper.”

6. • The early Greek civilisation was probably the earliest to
concern itself with acoustics and the control of sound.
• The Roman writerVitruvius [181] studied these Greek
designs and gave detailed descriptions of “several
acoustic calculations and contrivances” and
“prescriptions as
to the size and proportions of the stage and the plan for
the spectators” to ensure “the voice will meet with no
obstruction.”
• He wrote also of harmonics and on the design and use of
bronze sounding vessels to reinforce speech at various
frequencies as employed “in a good many Greek states.

7. • Dense, massive, materials, such as concrete or brick, tend
to transmit sound waves through the material.
• High frequency sound waves (think of a high whistle) are not
capable of being transmitted through massive, heavy, material.
•
• Low frequency sound waves (bass) are transmitted through
massive materials.

8. An anechoic chamber is a space in which there are no echoes or
reverberations.
The surfaces absorb all sound, and reflect none.

9. Resonance & sympathetic vibration
The harmonic series
Standing waves in a solid (e.g., string)
Interference & beats
• Chorus effect
Harmonics (on bowed strings) show:
• Modes of vibration
• Node
• Relationship to sulponticello?
Architectural acoustics
• Resonance (as in I Am Sitting in a Room)
• Standing waves in air
Acoustic Phenomena

10. Bonded acoustical cotton; recycled cotton, class A
non flammable
Melamine FoamAcoustical Panels: fiber free, Class
A fire retardent

11. Fabric wrapped panels provide good acoustical absorption