Acoustics Module 4

ARCH 255 EVANGELISTA

SOUND

AMPLIFICATION

SYSTEMS


INTRODUCTION

There are several architectural

methods to increase sound

levels in a room…

However, in certain situations,

the use of Sound Amplification

Systems is encouraged and

sometimes necessary:

the distance from sound source to receiver exceeds 15m

the room is filled to capacity

the room is heavily treated with sound absorbing finishes

high prevailing background noise levels

low voice intensity of sound source


The design and installation of sound amplification systems

involve several disciplines including:

Mechanical and electrical

consultants: involved with the

provision of electrical power

supplies and cable routes

Electronic consultants: involved

with the sound requirements,

specifications, equipment

performance, etc.

Theater consultants: involved

with how the sound system

interfaces with their respective

areas of concern

Acoustical consultants: involved

with structural isolation, material

finishes, reverberation time, etc.

The Architect: concerned with the

overall integration of the sound

system into the project design (i.e.

loudspeaker types, placement and

location, appearance, etc.)

INTRODUCTION


Sound systems should meet the following criteria:

1. Sound amplification systems should properly transmit

a wide range of frequencies (32-12000 Hz)

to maintain a correct balance between fundamentals and

harmonics

to achieve perfect tone color for each musical instrument

to provide clear, undistorted sound

SOUND AMPLIFICATION SYSTEMS



2. Sound amplification systems should provide a wide

dynamic range

a pianissimo sound must be clearly audible

a fortissimo sound must be reproduced without distortion


3. Sound amplification systems should create a

sufficiently low room reverberation


4. Sound amplification systems should be free from

disturbing echoes or feedback

FEEDBACK:

squealing or howling sounds;

occurs when…



radiated sound picked up

by the microphone reflective surfaces return

amplified sounds in reverberant rooms


5. Sound amplification systems should remain undetected.

The illusion should be preserved that amplified sound comes

from the natural sound source

The Time Delay between the arrival of

direct and amplified sound must not

exceed 20 to 25 msec

The distance between sound source

and loudspeaker should not exceed

7.0 to 8.0M



7 -8M

7 -8M


SYSTEM COMPONENTS

Sound amplification systems

have 3 basic components.

Microphone: picks up the

sound energy radiated by

the source, converts it into

electric energy and feeds it

into the amplifier

Amplifier: increases

magnitude of the electric

signal; delivers it to the

loudspeaker. May include

separate mixers.


Loudspeaker: converts the

electric signal into airborne

sound waves for distribution

to the listeners

COAXIAL UNITS

Sound amplification systems

have 3 basic components.

SYSTEM COMPONENTS

SUBWOOFER

loudspeaker dedicated to the

reproduction of low-pitched audio

frequencies known as bass

loudspeaker system in which the

individual driver units radiate sound

from the same point or axis


LOUDSPEAKER SYSTEMS

Central Loudspeaker System:

uses a single cluster of loudspeakers over the sound

source. The preferred type because it gives maximum

realism.


LOUDSPEAKER SYSTEMS

Central Loudspeaker System:

provides the room with

even coverage


Cases where Central Loudspeaker System is impractical

The ceiling height is too low for the

Central System

Majority of the listeners do not have

an adequate sightline to the central

loudspeaker

LOUDSPEAKER SYSTEMS


Cases where Central Loudspeaker System is impractical

Sound has to be provided to

overflow audiences

The spaces are too large for a

Central System

The halls are divided into smaller

spaces

LOUDSPEAKER SYSTEMS


Distributed Loudspeaker System:

uses a number of low level overhead loudspeakers

located throughout the auditorium.

LOUDSPEAKER SYSTEMS


Artificial Echo:

Rear end of the hall receives

amplified sound way before

direct sound.

Sound Overlaps: Some areas

receive amplified sound from

more than one speaker

LOUDSPEAKER SYSTEMS




PROBLEMS

This may be overcome by a Time

Delay Mechanism


Sound Overlaps: Some areas

receive amplified sound from

more than one speaker

LOUDSPEAKER SYSTEMS




Speakers should be spaced 12-15m

apart when facing the same direction

Speakers should be spaced at least

25m apart when facing each other

Artificial Echo:

Rear end of the hall receives

amplified sound way before

direct sound.

PROBLEMS

This may be overcome by a Time

Delay Mechanism


Stereophonic System:

employs two or more microphones adequately spaced

in front of the performing area and connected through

separate amplifying channels to two or more

corresponding loudspeakers

LOUDSPEAKER SYSTEMS


Combination Central- Distributed Loudspeaker System:

uses a cluster of loudspeakers over the sound

source, plus additional speakers at the rear end of

the hall or under balconies.

LOUDSPEAKER SYSTEMS


Types of Loudspeakers

Line or Column:

concentrates most of the sound

in a narrow angular spread in the

vertical plane and a semi-narrow

spread in the horizontal plane.

LOUDSPEAKER SYSTEMS


Radial or Multicellular:

concentrates most of the sound

in a wide angular spread in both

the vertical and horizontal plane.

LOUDSPEAKER SYSTEMS

Types of Loudspeakers


HOMETHEATER SYSTEMS

Home Theater Systems have five basic components:

Sources: players, tuners, game

consoles, etc.

Receivers: A/V receivers, controllers,

decoders, power amplifiers, etc.

Displays: direct projector, rear

projector, flat panel, standard sized

televisions, computer monitors, etc.


HOMETHEATER SYSTEMS

Home Theater Systems have five basic components:

Speakers: front and side speakers,

surround sound speakers,

subwoofers

Connections: antennas, satellite,

cable connections, internet DSL

connections, etc.


Home Theaters have varying

set-up classifications:

2-channel systems: front left and

right speakers only.

HOMETHEATER SYSTEMS

Speakers should form an equilateral

triangle with the sweet spot.




Multi-channel (i.e. 5.0, 5.1, 6.1, 7.1):

front, side, and rear speakers. Set-

up relies heavily on encoding and

decoding technologies

HOMETHEATER SYSTEMS




HOMETHEATER SYSTEMS

Multi-channel (i.e. 5.0, 5.1, 6.1, 7.1):

front, side, and rear speakers. Set-

up relies heavily on encoding and

decoding technologies


Front speakers should be direct

radiating speakers.

Midrange speakers should be

located away from enclosures, while

Subwoofer locations are flexible, but

are best placed in corners.

Surround sound speakers may be

Dipole or Bipole, and may be placed

at the side or the rear.

HOMETHEATER SYSTEMS




Furniture should not be placed

between the sound paths.

Room proportions are critical for

good sound diffusion. Ideally , the

room is rectangular in shape, with

the short side equivalent to 2/3

the length of the long side. For

small square rooms, a diagonal

layout is ideal.

Tweeter heights of front speakers

should be within 300mm of each

other for a seamless, consistent

front soundstage

HOMETHEATER SYSTEMS




HOMETHEATER SYSTEMS

Room Acoustics

Requirements:

The most important consideration

is speech intelligibility.

Thus, of primary concern is

reducing or eliminating, first and

second reflections

This can be solved with acoustical

treatment at points of reflection.


HOMETHEATER SYSTEMS

Room Acoustics

requirements:

ABSORPTION COVERAGE


HOMETHEATER SYSTEMS

Sound Isolation

Soundproofing of Home Theaters

is achieved with 3 main concepts:

Mass - make walls heavier, or

provide multiple layers

Decoupling - preventing sound

transmission by physically

separating connections

Damping - to reduce sound and

vibration through absorption,

which in turn mitigate the

transmission of sound to an

adjacent room.


To reinforce sound levels in an auditorium

To provide amplified sound for overflowing audiences

To increase sound level on the stage of an auditorium

To provide sound in motion picture theaters

To reduce the masking effect of an excessive background

noise level in an auditorium

To provide sound effects

To provide artificial reverberation in dead halls

General purposes of Sound Systems:

SOUND SYSTEM USES


Electronic devices have several other uses:

To distribute radio and recording programs in factories, schools,

hospitals, hotels, restaurants, etc.

To provide paging and announcing facilities in offices,

stores, transportation buildings, hotels, etc.

To provide background music in stores, offices, elevators, etc.

To provide personal communicating facilities between

individuals in separate locations in a building

To provide simultaneous translation for certain conferences

For signalling time periods

To provide individual hearing aids in an auditorium

To operate electronic organs, chimes, and carillons

SOUND SYSTEM USES


REFERENCES:

Leslie L. Doelle. Environmental Acoustics

Cyril M. Harris. Noise Control in Buildings: A Practical Guide for Architects

and Engineers, 1994

William Cavanaugh. Architectural Acoustics: Principles and Practice, 2010

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Acoustics Module 4

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