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4. (a) Discuss in detail, using notes and freehand sketches, the importance of each of the following in reducing the transmittance of sound in a dwelling house: - mass - completeness - isolation - Leaving Cert Construction Studies - Question 4 - 2011
Question 4
4. (a) Discuss in detail, using notes and freehand sketches, the importance of each of the following in reducing the transmittance of sound in a dwelling house: - m... show full transcript
Worked Solution & Example Answer:4. (a) Discuss in detail, using notes and freehand sketches, the importance of each of the following in reducing the transmittance of sound in a dwelling house: - mass - completeness - isolation - Leaving Cert Construction Studies - Question 4 - 2011
Step 1
Discuss in detail, using notes and freehand sketches, the importance of mass in reducing the transmittance of sound.
Answer
Mass plays a critical role in sound insulation, as outlined by the Mass Law, which states that the sound insulation of a single leaf partition is proportional to its mass per unit area. In essence, a heavier partition will effectively reduce sound transmission.
- Impact of Mass: The more massive the wall, the greater the reduction in sound transmittance. For instance, the mass of partitions can attenuate sound by about 6 dB with an increase in mass.
- Practical Applications: Utilizing heavy materials, such as concrete blocks, enhances sound insulation, as does increasing the thickness of walls by adding layers of plasterboard.
- Considerations: Features like staggered studs and double-layer configurations can significantly reduce sound paths. Each layer contributes to further damping high-frequency sounds.
Step 2
Discuss in detail, using notes and freehand sketches, the importance of completeness in reducing the transmittance of sound.
Answer
Completeness is vital in creating effective sound insulation. An incomplete structure can provide minor pathways for sound to travel.
- Fabric and Structure: The fabric of the partition must be complete; small gaps can significantly lower sound insulation effectiveness.
- Junction Details: It is crucial to ensure that all joints, such as those connecting to doors or near electrical fixtures, are fully sealed to prevent sound leakage.
- Blockwork Considerations: Properly finished blockwork contributes to completeness, as any unsealed areas can serve as sound transfer points.
Step 3
Discuss in detail, using notes and freehand sketches, the importance of isolation in reducing the transmittance of sound.
Answer
Isolation prevents sound from traveling between adjoining spaces by creating physical barriers and using appropriate materials.
- Structure Isolation: Separate sound paths need to be designed to minimize interactions between the two sides of the wall. This can involve double structures or floating floors that absorb sound.
- Material Choices: For instance, using isolation pads or stands can decouple the structure and enhance sound insulation.
- Air Tightness: Ensuring that the structure is air-tight is essential; gaps need to be sealed with flexible acoustic gaskets to enhance isolation further.
Step 4
Discuss two possible reasons why sound might be transmitted between the houses.
Answer
Sound may be transmitted between the houses due to several structural inadequacies:
- Gaps in Construction: Poor workmanship may lead to gaps in mortar joints that are not completely filled, allowing sound to travel through these openings.
- Junction Issues: The junction of the party wall with adjoining side walls or roofs may not be properly sealed, enabling sound transmission across these joints.
Step 5
Show the revised design detailing that would improve the sound insulation properties of the party wall between both houses.
Answer
To enhance the sound insulation of the party wall, the following design modifications can be made:
- Increased Mass: Adding additional layers of plasterboard to the existing wall will enhance its mass and, consequently, its sound insulation capabilities.
- Absorption Material: Filling cavities with sound-absorbent materials, like mineral wool, will dampen sound further. The design should illustrate how these layers interact for optimum performance.
- Air-tightness: All gaps must be sealed using appropriate tapes and flexible sealants to maintain air-tightness and prevent sound leakage.
Step 6
To reduce the transmittance of sound through a timber stud partition, show notes and freehand sketches, and a revised design for the stud partition.
Answer
The redesign of the timber stud partition should include:
- Typical Construction: Use timber studs at 400 mm centers; each layer should comprise plasterboard of 2 x 12.5mm on each side, combined with 60 mm of mineral insulation between the studs.
- Layering for Mass: Increase the mass by adding an additional layer of plasterboard on one side, which can substantially reduce high-frequency sound transmission.
- Air-tight Details: Ensure that all edges are sealed, and introduce features like rubber seals for doors to prevent sound leakage through openings.