bu midterms exam

technology of designing spaces to meet
hearing needs

branch of acoustics that deals with
providing rooms and buildings with good
conditions for listening to speech and music

Basic elements ARCHITECTURAL ACOUSTICS

Whisper; quiet room
- Faint
- Will not cause damage
- Lawn mower, City Traffic
- In 4 hrselectric drill
- 1 hrpersistence of sound after the cause of
sound has stopped
caused when reflected sound at
sufficient intensity reaches a listener
approximately 70 msec or more
- annoying and make speech less
intelligibleused for reduction of noisethree families of devices for sound absorption:lime or gypsum binderwith incombustible mineral
binderlong wood fibermineral fibersFibrous materials combined with a
binder agent
- sprayed on with an air gun or blower.
most common: mineral wood, hair
felt, wood fiber. and glass fiber.
- Thickness of blankets: between 1
1/2 and 4 inches
- greater thickness are sometimes
used in special applicationsmost common: mineral wood, hair
felt, wood fiber. and glass fiber.
- Thickness of blankets: between 1
1/2 and 4 inches
- greater thickness are sometimes
used in special applicationsALUE OF J breaking direct connections between
building components, such as ceilings and
walls, to disrupt the path of vibrations and
minimize their impact.

Moderate rainfall; normal convo
- Moderator

Beginning of hearing damage
- After 8hrs of exposure

- Lawn mower, City Traffic
- In 4 hrs

hairdryer, garbage disposal
- 2 hrs

electric drill
- 1 hr

motorcycle
- 30 mins

mp3 player, snowmobile
- 15 minutes

leaf blower, stadium football game
- 30 seconds

rock concert, ambulance siren
- 8 seconds

fire alarm, firecracker

jet engine at take off, gunshot
- damage in immediate hearing

THEATER OF EPIDAURUS
- Spectators capacity:

CAVEA:
ORCHESTRA:
HEIGHT:

Seats: THEATER OF EPIDAURUS

persistence of sound after the cause of
sound has stopped

Old churches

should hear the speaker of performer with the
same degree of loudness and clarity

sound hits a surface that is neither
predominantly absorptive nor sound
transparent

sound reflects off a hard polished
surface

design procedure for analyzing
reflected sound distribution
throughout a hall
- using the first reflection

reflect sounds

caused when reflected sound at
sufficient intensity reaches a listener
approximately 70 msec or more
- annoying and make speech less
intelligible

focus reflected sound into
certain-areas of rooms
Ex: Concave domes, vaults, or walls
- will deprive some listeners of useful
sound reflection and cause hot spots
at other audience positions

converse of focusing and occurs
primarily when sound is reflected
from convex surfaces.
- provided
by flat horizontal inclined reflectors

reflection of sound along a curved
surface

used for reduction of noise

- The rate which sound is absorbed in a room
is a prime factor in reducing noise and
controlling reverberation.

three families of devices for sound absorption:

principal type of
material available for acoustical
treatment

mechanically perforated units
backed with absorbent material

TYPES OF ACOUSTICAL MATERIALS THREE (3) CATEGORIES:

pined or granular - appearing
surface.

with Portland cement binder.

lime or gypsum binder

with incombustible mineral
binder

perforated surface; in a regular
pattern

perforated surface (acts as a
covering and support)

circular perforations

slots or grooves

Units having a fissured surface
-VERMICULITE : GOOD
INSULATORS

felted fiber surface

long wood fiber

fine felted vegetable fiber or
wood pulp

mineral fibers

On materials
- comprise plastic and porous
materials applied with a trowel and
fibrous materials
- combined with binder agents

composed of a cementitious material
such as gypsum, portland cement,
or lime with or without an aggregate

Acoustic materials other than
acoustic plaster which are applied
with a trowel

Fibrous materials combined with a
binder agent
- sprayed on with an air gun or blower.

- mineral or wood wool, glass fibers,
kapok batts, and hair felt
- The physical characteristics of the
materials in each of these categories
will now be considered.

most common: mineral wood, hair
felt, wood fiber. and glass fiber.
- Thickness of blankets: between 1
1/2 and 4 inches
- greater thickness are sometimes
used in special applications

absorb the widest range of frequencies

allows you to create many different designs.
Install vertically, horizontally, diagonally,
checkerboard

Flat Surfaced

Convoluted or Flat Surface Pattern

Soft Textured Beaded Surface

Plain, mounted with fiberglass core
encapsulated in polyvinyl fil or sail cloth.

Quilted pattern made of Acoustical foam or
Fiberglass core

Soft gray, ideal behind acoustic fabric,
perforated or slotted panel surfaces

Non Abrasive, slightly textured, porous

Flat surface, vinyl noise barrier with
polyurethane foam vibration decoupler.

ACOUSTICAL DESIGN OF
ROOMS & THEATERS FLOOR PLAN

direct and reflected sound
give rise to echoes

produce a blurring quality
which may result in a lack of
"intimacy"

Angle of elevation of the room in an
auditorium i

CEILING
Large room =

CEILING Small room

a sloping or beveled surface
or angle as of the side of a
doorway, a spreading
expansion, enlargement

sound that travels through the air from its
source to a receiver

which travels through
physical structures like walls or floors

implementation of acoustic absorption
techniques

trap and reduce reverberation

sealing existing gaps and holes

CONTROLLING AIRBORNE NOISES (3)

Level of airborne sound insulation relies on the
following general principles:

transmission of sound through solid
structures

CONTROLING SOLIDBORNE NOISES

rigidly coupling the vibrating source
to a large mass(inertia block)

supporting the vibrating mass on
resilient supports.

a distance of 100 pipe diameters
beyond the pump resilient pipe

to structural elements
- absorb and convert vibrations into
heat

Formulate the Sabine’s formula

Sabine’s formula

VALUE OF K IN FT

VALUE OF K IN METER

period required for the sound level to
decrease 60 dB

HOW MANY DB FOR typical room background

DESIRABLE REVERBERATION TIME
Medium sized general purpose auditorium
Classroom
Restaurants
Multi Purpose

isolating structural elements
- through the use of resilient materials or
isolators strategically placed between
components

resilient underlayment or a floating floor
system, vibrations are absorbed

breaking direct connections between
building components, such as ceilings and
walls, to disrupt the path of vibrations and
minimize their impact.