# Building Construction Questions and Answers – Common Acoustical Defects

This set of Building Construction MCQs focuses on “Common Acoustical Defects”.

1. Which of the following is not an acoustical defect?
a) Reverberation
b) Formation of echoes
c) Absorption
d) Sound foci

Explanation: Some of the common acoustical defects are reverberation, the formation of echoes, exterior noise and sound foci. Absorption is the property of the sound wave by which a part of its energy is absorbed by friction when it strikes a surface.

2. Excessive reverberation is caused due to __________
a) Sufficient absorption
c) Insufficient absorption

Explanation: Excessive reverberation is caused due to insufficient absorption. Reverberation is the continuation of the sound in space even after the source of sound has been removed.

3. The formation of echoes can take place when the reflecting surfaces are located at a distance greater than __________
a) 7 m
b) 10 m
c) 13 m
d) 17 m

Explanation: The formation of echoes can take place when the reflecting surfaces are located at a distance greater than 17m. This defect can be removed by making surfaces highly absorbent.

4. Sound foci is a defect caused by _____________ interior surfaces.
a) Convex refracting
b) Concave refracting
c) Convex reflecting
d) Concave reflecting

Explanation: Sound foci is a defect caused by concave reflecting interior surfaces. It is because of the concentration of the reflected sound waves at certain spots. This defect can be removed by avoiding curvilinear interiors.

5. Sound intensity is high at dead spots while it is low at sound foci.
a) True
b) False

Explanation: Sound foci involves the concentration of sound waves at certain spots creating high sound intensity. Dead spots are the points where there is a deficiency of the reflected sound waves. Hence, sound intensity is high at sound foci and low at dead spots.
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6. Proper shape of the hall can help in preventing the formation of echoes.
a) True
b) False

Explanation: Echoes are formed due to the unsuitable shape of the hall/auditorium. Hence, the proper shape of the hall can help in preventing the formation of echoes.

7. Colouring of sound quality is caused due to _________
a) Uncontrolled resonance
b) Controlled resonance
c) Unsuitable shape of halls
d) Vehicles

Explanation: Coloring of sound quality is caused due to uncontrolled resonance. Another cause of this defect is selective absorption. In order to remove this defect, wood panel absorbents are used which resonate over a wide range of frequency.

8. The branch of science which deals with origin and propagation of sound is called as ___________
a) Thermodynamics
b) Acoustics
c) Anemology
d) Optics

Explanation: The branch of science which deals with origin and propagation of sound is called acoustics. Thermodynamics is the study of the flow of heat, anemology is the study of wind and optics is the branch of science dealing with the study of light.

9. Which of the following is not a property of good acoustic materials?
a) They have a low coefficient of absorption
b) They are comparatively cheap
c) They are durable
d) They are efficient over a wide frequency range

Explanation: Good acoustic materials are comparatively cheap and durable. They have a high coefficient of absorption and are efficient over a wide frequency range.

10. The absorption ratio of a surface is the ratio of ___________
a) Sound absorbed to reflected sound energy
b) Sound absorbed to incident sound energy
c) Reflected sound energy to incident sound energy
d) Incident sound energy to reflected sound energy

Explanation: The absorption ratio of a surface is the ratio of sound absorbed to incident sound energy. The sound reducing the effect of an absorber is dependent on its area and on the efficiency of the material. It is indicated by the sound absorption coefficient.

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