Acoustics

Question 1

Define Sound

Answer 1

Sound is a vibration or pressure wave that moves through a suitable medium such as air or structure at a frequency and intensity that can be detected by the human ear

Question 2

Define noise

Answer 2

unwanted sound

Question 3

What are building acoustics

Answer 3

the science of controlling noise in buildings

• Minimising noise transmission
• Controlling the characteristics of sound within spaces themselves

Question 4

Acoustic design, performance criteria

Answer 4

Sound must reach all parts of the room

An even distribution of sound

noise that masks required sound must be reduced

The rate of decay of sound within the room (Reverberation time) Should be the optimum for the required use of the room

Question 5

Define airborne Sound

Answer 5

Sound which travels through the air before reaching a partition

Question 6

Examples of airborne sound

Answer 6

Voices
Radio
Instruments
Traffic
Planes

Question 7

How to use NR chart

Answer 7

The highest point in the level taken

Question 8

Define impact sound

Answer 8

Generated as a result of impact or a continuous vibration against a part of a building partition

Question 9

Examples of impact sound

Answer 9

Footsteps
Doors slamming
Noisy pipes
Vibrating machinery

Question 10

Flanking Transmission

Answer 10

The sound transmitted between rooms via flanking elements instead of directly through separating elements or along any path other than the direct oath

Question 11

Flanking Element

Answer 11

any building element, such as walls, that contributes to sound transmission between rooms in a building that is not a separating floor or wall

Question 12

Leaks

Answer 12

Cracks at wall/floor junctions, electrical outlets
Transmits at a higher frequency

Question 13

Two methods of sound control

Answer 13

Sound absorption
Sound Insulation

Question 14

Sound Absorption

Answer 14

The reduction of sound energy reflected by the surfaces of a room

Question 15

Sound Insulation

Answer 15

Is the principal method of controlling both airborne and impact sounds in a building
Reduces sound energy transmitted into an adjoining air space

Question 15

Sound control: 4 general Principals

Answer 15

Mass
Completeness
Flexibility
Isolation

Question 16

Types of sound absorbers

Answer 16

Porous Absorbers
Panel Absorber
Cavity Absorber

Question 17

Porous Absorber

Answer 17

Consist of cellular materials such as fibre glass or mineral wool which possess an open pore structure

Sound waves loose energy as a result of frictional heat generated due to the resistance of air molecules in the pores

Question 18

Panel Absorber

Answer 18

Flexible sheets or rigid panels with a space behind then which may contain a porous abdorbent or air

Question 19

Cavity Absorber

Answer 19

Are air containers which have a narrow opening.

When the air in the cavity is forced to vibrate energy from the sound waves are removed due to the drag of air

Question 20

Perforated panel absorber

Answer 20

For wide range frequencies
They use all3 methods. They have cellulous insulation, A panel with a space behind it and gaps

Question 21

Reverberation

Answer 21

The continuation and enhancement of a sound caused by multiple reflections between surfaces of a room

Question 22

Reverberation Time

Answer 22

A measure of how long it takes for sound to die away.
The time taken for a sound when stopped to decay by 60dB

Question 23

Reverberation time depends on

Answer 23

Areas of Exposed surfaces
Sound absorption properties of the surfaces
Distances between the surfaces
Frequency of the sound

Question 24

Control of reverberation time

Answer 24

Adding sound absorbing materials

Question 25

Reverberation time Formula

Answer 25

T= 0.16V
A

Question 26

Unit of Reverberation time

Answer 26

m2 Sabins