# Building Construction Questions and Answers – Acoustics – Sound Insulation

This set of Building Construction Multiple Choice Questions & Answers (MCQs) focuses on “Acoustics – Sound Insulation”.

1. Calculate the transmission loss given the sound levels measured on either side of the wall is 60 dB and 40 dB.
a) 20 dB
b) 100 dB
c) 60 dB
d) 2400 dB

Explanation: Reduction in the sound intensity during the transmission of sound from the source to the adjoining area is known as transmission loss. The transmission loss is numerically equivalent to the loss in the sound intensity in decibels. Hence, it is given by 60-40 dB = 20 dB.

2. Hard materials used for sound insulation are good absorbers.
a) True
b) False

Explanation: Sound insulation is a measure which is used to reduce the level of sound when it passes through an insulating component of the building. Hard materials that are used for sound insulation are poor absorbers. However, sound absorbers are poor sound insulators.

3. The sound insulation of plastered solid brick masonry walls varies as __________
a) Weight per unit volume
b) Weight per unit area
c) Log of weight per unit volume
d) Log of weight per unit area

Explanation: The sound insulation of plastered solid brick masonry walls varies as the log of weight per unit area. The sound insulation of all the other non-porous homogeneous rigid partitions varies in the same way.

4. Felt and mineral wool are examples of ___________
a) Non-porous rigid partitions
b) Porous rigid materials
c) Non-rigid porous materials
d) Non-rigid non-porous materials

Explanation: Felt and mineral wool are examples of non-rigid porous materials. These materials are not usually used for the purpose of noise reduction because the sound insulation provided by them is low as compared to the rigid materials.

5. In rigid homogeneous walls, the transmission loss of a one-brick wall is _________
a) 10 dB
b) 20 dB
c) 50 dB
d) 70 dB

Explanation: In rigid homogeneous walls, the transmission loss of a one-brick wall is 50 dB. The transmission loss of a one and a half brick thick wall is 53 dB and that of a half brick thick wall having 13 mm thick plaster on both sides is 45 dB.
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6. In cavity wall construction for soundproofing, the width of the cavity should be at least _________
a) 3 cm
b) 5 cm
c) 8 cm
d) 12 cm

Explanation: In cavity wall construction for soundproofing, the width of the cavity should be at least 5 cm. This type of construction ideal from the point of view of soundproofing. The cavity is either left air-filled or filled with some resilient material.

7. The sound insulation offered by rigid homogenous walls decreases with the increase in the thickness of the wall.
a) True
b) False

Explanation: A rigid wall is comprised of stone, brick or concrete masonry plastered on one or both sides. The sound insulation offered by rigid homogenous walls depends on the weight per unit area and it decreases with the increase in the thickness of the wall.

8. Insulation of __________ over a base concrete floor is obtained by using resilient surface material on floors.
a) 1-5 dB
b) 5-10 dB
c) 12-15 dB
d) 17-25 dB

Explanation: An insulation of 5-10 dB over a base concrete floor is obtained by using resilient surface material on floors. It consists of providing soft floor finish over a thin concrete screed provided as the R.C.C. slab.

9. Concrete floor floating construction provides good insulation against __________ sounds.
a) Impact
b) Air-borne
c) Water-borne
d) Structural

Explanation: Concrete floor floating construction provides good insulation against impact sounds. In this type of construction, an additional floor is constructed and isolated from the already existing concrete floor.

10. Which of the following constructions is effective against both air-borne and structure-borne sounds?
a) Timber floor floating construction
b) Use of resilient surface material
c) Timber floor with suspended ceiling and air space
d) Concrete floor floating construction

Explanation: Timber floor with suspended ceiling and air space construction is effective against both air-borne and structure-borne sounds. The extent of improvement effected is dependent on the weight of the ceiling and on the structural rigidity.

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