EP UNIT-2 Acoustics

Question 1

What are Sound waves?

Answer 1

Mechanical Vibrations of smaller amplitude

Question 2

What are the three different categories for sound?

Answer 2

Infrasonic - F < 20 Hz
Ultrasonic - F > 20 kHz
Audible Sound - 20Hz >= F =< 20kHz

Question 3

What is the difference between ‘Musical Sound’ and ‘Noise’

Answer 3

Musical Sound - Produces a pleasing effect on the ear
Noise - Jarring and unpleasant effect on the ear

Question 4

What is Pitch?

Answer 4

It is the sensation conveyed to our brain by the sound waves falling in our ears.
Frequency is the physical quantity while Pitch is the physiological quantity.

Question 5

What is the ‘Quality’ of sound?

Answer 5

The ability to distinguish between different sounds, like musical instruments or voices, even when they have the same pitch and loudness

Question 6

What is the ‘Intensity’ of sound?

Answer 6

The average rate of flow of acoustic energy per unit area situated normally to the direction of the propagation of sound waves.
I = Q/A

Question 7

What is ‘Loudness’?

Answer 7

The degree of sensation produced on the ear.
It is a physiological quantity.
L = k log(I)

Question 8

What is the Absorption Coefficient?

Answer 8

The reciprocal of its area that absorbs the same amount of sound energy as absorbed by a unit area of an open window.
Absorption Coefficient = Sound energy absorbed by the surface/ Total sound energy incident on the surface

Question 9

How many Factor are there affecting the Acoustics of a Building?

Answer 9

6

Question 10

What are the Factors affecting the Acoustics of a Building?

Answer 10

1) Optimum Reverberation Time
The time it takes for the sound to fall one-millionth of its original intensity.
If the Reverberation time is high -> Echoes form
If the Reverberation time is low -> Sound is not clear and audible

2) Loudness
The degree of sensation produced on the ear varies for each person and could vary in different places in the same building

3) Focusing & The Interference Effect
Due to Constructive or Destructive interference caused by external or internal sounds causing uneven distribution of sound intensity

4) Echoes & The Echelon Effect
How the sound wave is scattered after reflecting off the wall of the building which causes echoes. Echoes are created when the time intercval between the directed and reflected sound wave are approximately 1/15th of a second. Repetition of echoes are called the “Echelon effect”

5) Resonance
A frequency of a sound matches with the standard natural audio frequency that results in interference occurring and another sound being formed or amplified.

6) Noise
(1) Airborne noise -> noise that enters through open windows, doors, ventilation
(2) Structure Borne Noise -> noise that enters through the structure of the building
(3) Inside Noise -> Noises produced inside the building.